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Men's health Women's health Preventative medicine Endocrine and metabolic Musculoskeletal

Vitamin D deficiency in adults

Last revised in August 2026

Vitamin D is a fat soluble vitamin that regulates calcium and phosphate homeostasis and is therefore vital for musculoskeletal health.

Vitamin D deficiency in adults: Summary

  • Vitamin D is a fat-soluble vitamin that regulates calcium and phosphate homeostasis and is therefore vital for musculoskeletal health.
  • Vitamin D circulates in the blood as both vitamin D3 (colecalciferol) and vitamin D2 (ergocalciferol).
    • Vitamin D is mainly derived from skin exposure to ultraviolet B radiation from sunlight. The remainder is provided by dietary sources.
  • Recommended vitamin D thresholds in the UK in respect to bone health are:
    • An increased risk of vitamin D deficiency occurs at serum 25-hydroxyvitamin D (25[OH]D) levels less than 25 nmol/L.
    • Vitamin D levels may be inadequate (or insufficient) in some people when serum 25(OH)D is 25–50 nmol/L.
    • Vitamin D levels are sufficient for most people when serum 25(OH)D is greater than 50 nmol/L.
  • Risk factors for vitamin D deficiency include people:
    • Aged 65 years and over.
    • Who have low or no exposure to the sun, for example, those who cover their skin; who are housebound or confined indoors for long periods.
    • Who have darker skin pigmentation.
    • With a malabsorption disorder, or following weight loss surgery.
    • With severe liver or end-stage chronic kidney disease.
    • Taking certain drugs.
    • Who are pregnant or breastfeeding.
    • With obesity.
  • Complications of vitamin D deficiency include increased risk of:
    • Osteomalacia — may present with lower back pain, bone pain in the shoulder, ribs, pelvis, or legs; muscle pain and weakness; waddling gait; and impaired physical function.
    • Osteoporosis.
    • Falls and fragility fracture.
  • Assessment for vitamin D deficiency (by checking serum 25[OH]D levels) should be arranged if a person has:
    • Musculoskeletal symptoms that may be attributable to vitamin D deficiency.
    • Suspected bone disease such as osteomalacia or osteoporosis that may be improved with vitamin D treatment.
    • Known bone disease such as osteoporosis or Paget's disease, where correction of vitamin D deficiency is needed prior to specific treatment.
  • Management of a person with vitamin D deficiency includes:
    • Seeking specialist advice or arranging referral if the person has a condition predisposing to hypercalcaemia; a malabsorption disorder; renal stone disease; severe kidney or liver disease.
    • Providing advice on sources of information and support.
    • Advising on safe sunlight exposure and dietary sources of vitamin D.
    • Prescribing a fixed loading dose followed by maintenance vitamin D therapy for people needing rapid treatment.
    • Prescribing maintenance dose vitamin D therapy for people needing less urgent treatment.
    • Assessing dietary calcium intake and the need for supplementation.
    • Arranging follow up to reassess serum calcium and vitamin D levels (if clinically indicated).
  • Advice for the prevention of vitamin D deficiency should include:
    • Information on safe sunlight exposure and dietary sources of vitamin D.
    • Adults with risk factors should take a daily supplement containing 400 international units (IU) of vitamin D throughout the year.
    • Other adults should consider taking a daily supplement containing 400 IU of vitamin D, particularly in the autumn and winter.

Have I got the right topic?

From age 18 years onwards.

This CKS topic covers the diagnosis and management of adults with vitamin D deficiency and inadequate (or insufficient) vitamin D levels caused by inadequate sunlight exposure or nutritional deficiency. It also covers the prevention of vitamin D deficiency in adults.

This CKS topic does not cover the management or prevention of vitamin D deficiency in children.

There are separate CKS topics on Hypercalcaemia, Osteoporosis - prevention of fragility fractures, and Vitamin D deficiency in children.

The target audience for this CKS topic is healthcare professionals working within the NHS in the UK, and providing first contact or primary healthcare.

How up-to-date is this topic?

Changes

August 2026 — reviewed. A literature search was conducted in August 2026 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. The recommendation to seek specialist advice in pregnancy has been clarified, and a recommended daily dose to manage vitamin D deficiency in pregnancy has been added.

Previous changes

January 2022 — minor update. Broken link replaced for advice on vitamin D preparations for people on a halal or kosher diet. 

October 2021 — minor update. The dose of vitamin D required for maintenance therapy has been repeated for clarity in the recommendations for people not requiring a loading dose. 

March to April 2021 — reviewed. A literature search was conducted in February 2021 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. The topic title has been shortened to 'Vitamin D deficiency in adults'. The recommendations have been updated in line with current evidence in the literature. The recommendation on who should take year-round vitamin D supplementation for the prevention of vitamin D deficiency has been amended, in line with Public Health England (PHE) guidance. The section on Calcium and vitamin D combination products has been removed from the Prescribing information section to avoid repetition with text in the Management section.

December 2020  — minor update. The vitamin D level threshold below which musculoskeletal complications may occur has been updated in line with the UK Scientific Advisory Committee on Nutrition (SACN). A previously cited US Institute of Medicine (IOM) reference has been removed.

September 2018 — minor update. The recommendation on who to treat has been changed in line with the Scientific Advisory Committee on Nutrition (SACN) guidelines (SACN, 2016).

December 2016 — minor update. Ergocalciferol 1.25 mg (50,000 IU) capsules have been added to the section on product availability (ABPI, 2016). Desunin® (colecalciferol) 100 micrograms (4,000 IU) tablets have been added to the section on product availability in line with the British National Formulary (BNF, 2016).

August to November 2016 — new topic. The evidence base has been reviewed in detail, and recommendations are clearly justified and transparently linked to the supporting evidence.

Update

New evidence

Evidence-based guidelines

No new evidence based guidelines since 1 August 2026.

HTAs (Health Technology Assessments)

No new HTAs since 1 August 2026.

Economic appraisals

No new economic appraisals relevant to England since 1 August 2026.

Systematic reviews and meta-analyses

No new systematic reviews or meta-analysis which reach the CKS threshold for inclusion since 1 August 2026.

Primary evidence

No new primary evidence which reaches the CKS threshold for inclusion published since 1 August 2026.

New policies

No new national policies or guidelines since 1 August 2026.

New safety alerts

No new safety alerts since 1 August 2026.

Changes in product availability

No changes in product availability since 1 August 2026.

Goals and outcome measures

Goals

To support primary healthcare professionals to:

  • Be aware when to assess for vitamin D deficiency and insufficiency in adults.
  • Provide advice on management of vitamin D deficiency and insufficiency in adults.
  • Arrange referral to an appropriate specialist if indicated.
  • Provide advice on the prevention of vitamin D deficiency in adults.

Outcome measures

No outcome measures were found during the review of this topic.

Audit criteria

No audit criteria were found during the review of this topic.

QOF indicators

No QOF indicators were found during the review of this topic.

QIPP - options for local implementation

No QIPP indicators were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

Background information

What is it?

  • Vitamin D is a fat-soluble vitamin that regulates calcium and phosphate homeostasis and is vital for musculoskeletal health.
    • It promotes the absorption of calcium and phosphorus from the bowel and enables mineralization of newly formed osteoid tissue in bones, as well as having a role in neuromuscular function. 
  • Vitamin D circulates in the blood as both vitamin D3 (colecalciferol) and vitamin D2 (ergocalciferol). 
    • Vitamin D3 is synthesized in the skin from 7-dehydrocholesterol (7-DHC is a form of cholesterol naturally found in the skin) by the action of sunlight containing ultraviolet B (UVB) radiation (or by artificial UVB light). 
    • Both vitamin D3 and D2 can be obtained from natural foods (limited source), fortified foods, and food supplements. 
  • Dietary and skin-derived vitamin D are biologically inactive and require enzymatic conversion to the active metabolite 1,25-dihydroxyvitamin D (1,25[OH]2D). 
    • Vitamin D is converted in the liver to 25-hydroxyvitamin D (25[OH]D), the main circulating metabolite. This is then converted to 1,25(OH)2D in the kidneys and other tissues. The production of 1,25(OH)2D is regulated by the action of parathyroid hormone (PTH) on the kidneys.
  • Recommended vitamin D thresholds in the UK in respect to bone health are:
    • An increased risk of vitamin D deficiency occurs at serum 25(OH)D levels less than 25 nmol/L. 
    • Vitamin D levels may be inadequate (or insufficient) in some people when serum 25(OH)D is between 25–50 nmol/L. 
    • Vitamin D levels are sufficient for most people when serum 25(OH)D is greater than 50 nmol/L.

[SACN, 2023]

What causes it?

Vitamin D is mainly derived from skin exposure to ultraviolet B radiation from sunlight. The remainder is provided by dietary sources.

  • The amount of vitamin D synthesized in the skin can be affected by environmental factors:
    • Season, time of day, and weather conditions — solar UV levels are highest in the UK spring and summer months (between late March/early April and September), around midday, and are reduced by cloud cover. As a result, sunlight-induced vitamin D synthesis is only effective between these months in the UK. 
    • Latitude — at latitudes above 37º N such as in the UK, sunlight containing UVB radiation is limited in the winter months.
  • The amount of vitamin D synthesized in the skin can be affected by individual factors:
    • Age — lower serum 25-hydroxyvitamin D (25[OH]D) concentrations have been reported in older people compared with younger people. This is possibly because the amount of 7-dehydrocholesterol (7-DHC) present in the skin decreases with increasing age. Low 25(OH)D levels could also be due to the tendency for older people to wear more clothes, spend more time indoors, and develop medical conditions that can affect the activation or bioavailability of vitamin D (such as kidney or liver disease). 
    • Skin colour — melanin pigment absorbs a proportion of the UVB radiation needed for skin synthesis of vitamin D. People with dark skin may therefore need more sunlight exposure to produce the same amount of vitamin D as people with lighter skin pigmentation. 
    • Clothing cover — clothes that cover the entire body and face reduce skin exposure to sunlight. 
    • Sunscreen use — although it has been theorized that sunscreen use can significantly reduce vitamin D production, the Scientific Advisory Committee on Nutrition notes that the majority of people do not apply sunscreen at the recommended concentration, and do not apply it to all exposed areas of the skin. It states that normal usage of sunscreens does not generally prevent vitamin D synthesis, and that overall the data suggest that vitamin D synthesis is still possible even when sunscreens are used at the application density used for SPF testing. 
  • In the winter months in the UK, vitamin D has to be obtained from body stores (from UVB exposure in the summer months) and dietary sources.
    • There are few naturally rich food sources of vitamin D, and most contain vitamin D3. Sources include egg yolk, oily fish (such as salmon, mackerel, herring, and sardines), wild mushrooms, red meat, fat, liver, and kidney.
    • Vitamin D-fortified foods include most margarines and fat spreads, and some dried or evaporated milks and breakfast cereals. 
    • Vitamin D3 supplements are synthesized by UVB irradiation of 7-DHC from sheep wool, and vitamin D2 by UVB irradiation of ergosterol from fungi. 
  • Specific medical conditions may impair the absorption or activation of vitamin D [Holick, 2017] [Aoun, 2020].
    • Intestinal malabsorption syndromes (such as coeliac disease, cystic fibrosis, and Crohn's disease), or following weight loss surgery, impair the absorption of dietary vitamin D, leading to decreased bioavailability [Holick, 2017; Aoun, 2020]. 
    • Obesity (body mass index [BMI] greater than 30 kg/m2) is associated with lower vitamin D levels. This is likely to be multifactorial, including insufficient dietary intake of vitamin D, reduced sun exposure, diminished 25-hydroxylase activity, and changes in the gut microbiome [Demay, 2024]. 
    • End-stage chronic kidney disease (CKD) impairs the production of sufficient 1,25-dihydroxyvitamin D (1,25[OH]2D). 
    • Severe liver disease may affect the production of 25-hydroxyvitamin D (25[OH]D). 
    • Inherited enzyme disorders are rare and include mutation of renal 25-hydroxyvitamin D 1 alpha-hydroxylase (which causes vitamin D-deficiency rickets). 
  • Some drugs increase the risk of vitamin D deficiency [Preston, 2026]. 
    • Drugs that reduce fat absorption (for example, orlistat) can lead to a decreased bioavailability of vitamin D.
    • Antiepileptic drugs (especially carbamazepine, phenobarbital, and phenytoin), colestyramine, rifampicin, corticosteroids, thiazide diuretics, digoxin, calcium-channel blockers, and antacids. See the section on Drug interactions in Prescribing information for more information [Aoun, 2020].

[NICE, 2023; SACN, 2023]

What are the risk factors?

How common is it?

The prevalence of vitamin D deficiency varies in the literature depending on the definitions of deficiency and insufficiency used, the study population characteristics and geographical location, and laboratory assays used. 

  • According to the UK National Diet and Nutrition Survey, which reported low vitamin D status as indicated by serum 25-hydroxyvitamin D (25[OH]D) concentrations below 25 nmol/L [OHID, 2025]:
    • From 2019 to 2023, 18% of adults aged 19–64 years and 12% of adults aged 65 years and over had a serum 25(OH)D concentration below 25 nmol/L. 
    • The percentage of the population with serum 25(OH)D concentrations below 25 nmol/L was highest from January to March, and ranged between 21–38%, falling to between 0–10% in the summer months (July to September).
    • The prevalence of deficiency is marginally greater (3 percentage points) in men than women.
  • A UK longitudinal analysis of a primary care database (n = 6,416,709 adults) with a mean follow up of 5.4 years found [Crowe, 2019]:
    • One-third of participants tested for vitamin D deficiency had a serum vitamin D level less than 30 nmol/L.
    • Among ethnic minority groups, deficiency ranged from 43% among mixed ethnicity to 66% in Asians.
    • Being male, younger, and more economically deprived were also all associated with vitamin D deficiency.
  • An analysis of population data from 14 European nutrition and health surveys (n = 55,844 individuals) reported [Cashman, 2016]:
    • An overall pooled prevalence estimate, irrespective of age group, ethnic mix, and latitude of study populations, of serum 25(OH)D concentrations less than 30 nmol/L on average in the year was 13% of the population, with 17.7% and 8.3% in those sampled during the extended winter (October–March) and summer (April–November) periods, respectively.
    • The overall pooled prevalence estimate of serum vitamin D less than 50 nmol/L was 40.4%.
    • Dark-skinned ethnic subgroups had much higher (3- to 71-fold) prevalence of serum vitamin D less than 30 nmol/L than did white populations.

What is the prognosis?

  • Management of vitamin D deficiency and correction of modifiable risk factors should:
    • Restore vitamin D levels.
    • Reduce the risk of, or improve the symptoms of complications of vitamin D deficiency.
  • Following treatment for vitamin D deficiency or insufficiency, lifestyle changes and vitamin D supplementation are likely to be needed long term to maintain optimum vitamin D levels.

[SACN, 2023; Demay, 2024]

What are the complications?

The risk of musculoskeletal complications of vitamin D deficiency is increased at plasma 25-hydroxyvitamin D (25[OH]D) concentrations below 25 nmol/L. 

  • Osteomalacia and osteoporosis — prolonged severe vitamin D deficiency results in the bony skeleton becoming the body's main source of calcium, with osteoclasts breaking down bone to increase serum calcium levels. Osteomalacia is characterized by replacement of resorbed bone with unmineralized osteoid. Osteomalacia may subsequently precipitate or exacerbate osteopenia and osteoporosis. See the CKS topic on Osteoporosis - prevention of fragility fractures for more information.
    • Osteomalacia may present with lower back pain, bone tenderness or pain in the spine, shoulder, ribs, or pelvis, or legs; muscle weakness; waddling gait; and impaired physical function. 
  • Falls and fragility fractures — vitamin D deficiency or insufficiency may lead to secondary hyperparathyroidism, bone loss, reduced muscle strength and function, and increased risk of falls and fragility fractures in older people. See the CKS topics on Falls - risk assessment and Hypercalcaemia for more information.
    • CKS notes there is a lack of consistent evidence that vitamin D supplementation improves musculoskeletal outcomes such as bone density, fracture prevention, muscle strength, or falls risk [Avenell, 2021; Bolland, 2021; SACN, 2023].
  • Other complications — low levels of vitamin D have been associated with an increased risk of a variety of common non-musculoskeletal disorders, such as metabolic, cardiovascular, malignant, autoimmune and infectious diseases. However, a causal link has not been established.
    • Results from randomized controlled trials on vitamin D supplementation are inconsistent. 

[LeFevre, 2018; SACN, 2023; Demay, 2024]

Diagnosis

When should I suspect or test for vitamin D deficiency?

  • Do not routinely test for vitamin D deficiency in asymptomatic people.
    • Asymptomatic people at higher risk of vitamin D deficiency do not need routine testing for vitamin D deficiency, but should be advised on the need for maintenance-dose vitamin D supplementation. See the section on How to treat for more information.
  • Check the vitamin D level by measuring serum 25-hydroxyvitamin D (25[OH]D) if a person has:
    • Musculoskeletal symptoms (such as bone pain, myalgia, and generalized weakness) that may be attributable to vitamin D deficiency, or chronic widespread pain with other features of osteomalacia (such as proximal muscle weakness). 
    • Suspected bone disease that may be improved with vitamin D treatment, such as osteomalacia or osteoporosis. See the CKS topic on Osteoporosis - prevention of fragility fractures for more information. 
    • Known bone disease, where correction of vitamin D deficiency is needed prior to specific treatment, such as: 
      • Prior to osteoporosis treatment with a potent antiresorptive agent (zoledronate, denosumab, or teriparatide).
      • Prior to Paget's disease treatment with a bisphosphonate.

Basis for recommendation

These recommendations are based on the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the Endocrine Society guideline Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline [Demay, 2024], the National Osteoporosis Guideline Group (NOGG) guideline The 2024 UK clinical guideline for the prevention and treatment of osteoporosis [NOGG, 2025], and expert opinion in narrative reviews Vitamin D screening and supplementation in community-dwelling adults: common questions and answers [LeFevre, 2018], and When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020].

Asymptomatic people

  • There is insufficient evidence to recommend screening the general population for vitamin D deficiency, as treating asymptomatic people with identified vitamin D deficiency has not been shown to improve health outcomes [LeFevre, 2018; Aoun, 2020; Demay, 2024].

How to test

  • Serum 25-hydroxyvitamin D (25[OH]D) is the best clinical indicator of vitamin D status. It reflects both skin synthesis and dietary sources of vitamin D, has a fairly long half-life of 2–3 weeks, and is not subject to tight homeostatic control. As a result, it gives an indication of vitamin D availability over recent weeks [SACN, 2023].
    • In contrast, the active circulating metabolite serum 1,25(OH)2D concentration is a poor indicator of vitamin D status because it has a short half-life (4–15 hours); it is homeostatically regulated; the plasma concentrations are not directly regulated by vitamin D intake (but by other factors, such as plasma parathyroid hormone [PTH] levels); and even in the presence of severe vitamin D deficiency, plasma concentrations may be normal or even elevated.

What additional investigations should I arrange?

If vitamin D deficiency or insufficiency is diagnosed following blood testing, consider arranging additional investigations:

Basis for recommendation

These recommendations are based on expert opinion in a narrative review When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020]. They are also pragmatic, based on what CKS considers to be good clinical practice.

  • Vitamin D deficiency is usually accompanied by normal serum levels of calcium and phosphorus, high-normal or elevated levels of parathyroid hormone (PTH), and normal to elevated levels of total alkaline phosphatase. People with severe and longstanding vitamin D deficiency may occasionally present with overt hypocalcaemia and/or hypophosphataemia [Aoun, 2020].

What else might it be?

  • Conditions that may present similarly to vitamin D deficiency with bone pain and/or muscle weakness include:
    • Bone fracture — pain, swelling, or bruising over a bone, and bone deformity. 
    • Fibromyalgia — suspect if numerous myofascial trigger points and somatic symptoms are present.
    • Hyperparathyroidism — presents with symptoms of hypercalcaemia such as bone pain, muscle weakness, nausea, anorexia, renal stones, cardiac arrhythmias, depression, and cognitive impairment. See the CKS topic on Hypercalcaemia for more information.
    • Malignancy
    • Muscular dystrophies — cause progressive degeneration and muscle weakness. 
    • Osteomyelitis — severe pain, systemic symptoms, and functional impairment; soft tissue swelling and bony tenderness. 
    • Paget's disease of the bone — dull pain aggravated by weight-bearing and asymmetrical bowing of weight-bearing bones (especially tibia, femur, and forearm); usually affects elderly men. 
    • Polymyalgia rheumatica — bilateral shoulder and/or pelvic girdle pain and prolonged stiffness after waking or periods of rest; usually occurs in people aged over 50 years of age. See the CKS topic on Polymyalgia rheumatica for more information.
    • Polymyositis and dermatomyositis — autoimmune connective tissue diseases that may present with skin rash and progressive muscle weakness; may be associated with systemic symptoms. 
    • Rheumatoid arthritis — pain, swelling, heat (synovitis), and stiffness typically in the small joints of the hands and feet; may be associated with general malaise. See the CKS topic on Rheumatoid arthritis for more information.
    • Thyroid disease — may present with fatigue and muscle weakness. See the CKS topics on Hyperthyroidism and Hypothyroidism for more information.

Basis for recommendation

This information is based on the National Institute for Health and Care Excellence (NICE) guidelines Hyperparathyroidism (primary): diagnosis, assessment and initial management [NICE, 2019], and Suspected cancer: recognition and referral [NICE, 2026], and expert opinion in a narrative review When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020]. They are also pragmatic, based on what CKS considers to be good clinical practice.

Management

Scenario: Management of vitamin D deficiency or insufficiency

From age 18 years onwards.

When should I advise treatment of vitamin D deficiency or insufficiency?

If a person has been tested for vitamin D deficiency and results show:

Basis for recommendation

These recommendations are based on the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the National Institute for Health and Care Excellence (NICE) guideline Sunlight exposure: risks and benefits [NICE, 2023], and the National Osteoporosis Guideline Group (NOGG) guideline The 2024 UK clinical guideline for the prevention and treatment of osteoporosis [NOGG, 2025]. 

How should I treat vitamin D deficiency or insufficiency?

If a person needs treatment for vitamin D deficiency:

  • Seek specialist advice or arrange referral before starting vitamin D treatment if a person:
    • Has a medical condition that predisposes to hypercalcaemia, such as granulomatous disease (sarcoidosis, tuberculosis), metastatic bone disease, some lymphomas, or primary hyperparathyroidism, as there is an increased risk of vitamin D toxicity. See the CKS topic on Hypercalcaemia for more information.
    • Has a gastrointestinal or malabsorption disorder resulting in an inability to maintain adequate vitamin D status, as intensive high-dose replacement or maintenance treatment may be needed under specialist supervision. 
    • Has active renal stones or a history of renal stones, due to the risk of vitamin D toxicity causing hypercalciuria and renal stone disease. See the CKS topic on Renal or ureteric colic - acute for more information.
    • Has severe liver disease or end-stage chronic kidney disease (CKD), as specialist treatment with activated vitamin D metabolites may be needed. See the CKS topics on Chronic kidney disease and Jaundice in adults for more information.
    • Is pregnant — seek specialist advice in complex cases such as a history of rickets in a previous pregnancy, or if loading doses of vitamin D are considered necessary.
  • Advise that oral vitamin D3 is the vitamin D preparation of choice for the treatment of vitamin D deficiency, and vitamin D2 is an alternative option in some clinical situations. 
  • If rapid correction of vitamin D deficiency is needed, for example in people with symptoms or about to start treatment with a potent antiresorptive agent (zoledronate, denosumab, or teriparatide), prescribe a fixed loading dose followed by regular maintenance vitamin D therapy 1 month after loading.
    • The loading regimen should provide a total of approximately 300,000 international units (IU) of vitamin D, given either as separate weekly or daily doses over 6–10 weeks. See the section on Loading dose regimens in Prescribing information for more detailed information.
    • Maintenance therapy of vitamin D equivalent to 800–2000 IU daily (up to a maximum of 4000 IU daily for certain conditions such as malabsorption following specialist advice), given either daily or intermittently at a higher equivalent dose. 
    • Note: vitamin D may be prescribed for people with osteoporosis or a chronic condition or surgery that results in deficiency or malabsorption. Advise other people that maintenance therapy should be bought over the counter. 
  • If correction of vitamin D deficiency is less urgent and when co-prescribing vitamin D supplements with an oral antiresorptive agent, maintenance therapy (800–2000 IU daily) may be started without the use of loading doses. 
    • In pregnancy, consider a dose of 1000–2000 IU daily. A cumulative dose of 300,000 IU is necessary to correct deficiency. After correction, provide advice on preventing recurrence. 
    • Note: vitamin D may be prescribed for people with osteoporosis or a chronic condition or surgery that results in deficiency or malabsorption. Advise other people that maintenance therapy should be bought over the counter. 
  • Assess the person's need for calcium supplementation.
    • Assess the person's dietary calcium intake.
      • Consider using an online calcium calculator, such as the International Osteoporosis Foundation calcium calculator.
    • If the person has an inadequate calcium intake of less than 700 mg a day (more may be necessary if the person has osteoporosis), advise them to increase dietary calcium intake. 
    • If the person is unable or unwilling to increase dietary calcium intake, consider the need for calcium supplements. 
      • Seek specialist advice if there is any uncertainty regarding which calcium preparation to recommend. See the section on Available preparations in Prescribing information for more information.
      • The ROS leaflet Calcium includes a factsheet on calcium supplements that may be helpful.
  • Advise the person to maintain adequate vitamin D levels through safe sunlight exposure and diet. See the section on Lifestyle advice for more information. 
  • Arrange follow up for people with vitamin D deficiency to reassess serum calcium and vitamin D levels (if clinically indicated), and to check for ongoing symptoms. See the section on Follow up for more information. 

Basis for recommendation

These recommendations are based on the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], an international guideline Vitamin D supplementation guidelines [Pludowski, 2018], the National Osteoporosis Guideline Group (NOGG) guideline 2024 UK clinical guideline for the prevention and treatment of osteoporosis [NOGG, 2025], a Consensus statement on Vitamin D status assessment and supplementation: whys, whens, and hows [Giustina, 2024], the NHS Specialist Pharmacy Service (SPS) document Vitamin D deficiency: treatment during pregnancy [SPS, 2025a], the NHS England policy guidance Conditions for which over the counter items should not be routinely prescribed in primary care [NHS England, 2026], expert opinion in narrative reviews Diagnosis and management of vitamin D deficiency [Pearce, 2010], Vitamin D deficiency 2.0: an update on the current status worldwide [Amrein, 2020], and When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020], and the British National Formulary [BNF, 2026]. 

Seeking specialist advice or arranging referral
  • The recommendation that people with a medical condition that predisposes to hypercalcaemia should be referred is based an international publication [Pludowski, 2018] and expert opinion in narrative reviews [Amrein, 2020; Aoun, 2020].
    • These people and may need lower doses and more frequent monitoring, as they are at increased risk of vitamin D toxicity that manifests as hypercalcaemia.
  • The recommendation that people with a gastrointestinal or malabsorption disorder resulting in an inability to maintain adequate vitamin D status should be referred is based expert opinion in a narrative review, which notes that in adults with severe malabsorption treatment with intramuscular vitamin D may be needed to improve absorption and medication adherence [Pearce, 2010].
    • These people may require an individualized replacement or maintenance schedule under specialist supervision.
  • The recommendation that people with severe liver disease or end-stage chronic kidney disease (CKD) is based on an international publication, which notes that specialist treatment with activated vitamin D metabolites may be needed (calcifediol for liver disease, and alfacalcidiol or calcitriol for kidney disease) [Pludowski, 2018].
Vitamin D supplementation in pregnancy
  • ACOG advises that an optimal serum level of vitamin D during pregnancy has not been determined and when deficiency is identified most experts agree that 1000-2000 IU per day of vitamin D is safe. Higher dose regimens have not been studied in pregnancy [ACOG, 2011]. 
  • SPS advises that some vitamin D products are licensed for use in pregnancy, and that specialist advice should be sought for complex cases such as a history of rickets in a previous pregnancy [SPS, 2025a]. SPS recognises that there is no guidance available on duration of treatment in pregnancy, but a cumulative dose of 300,0000 IU is necessary with a daily dose of 1000–2000 IU, so correction of deficiency may take several months. 
  • UKTIS states there are insufficient data to provide recommendations on high-dose vitamin D for established vitamin D deficiency in pregnancy [UKTIS, 2026], and recognises that there are no official UK guidelines for treatment of vitamin D deficiency in pregnancy. UKTIS suggests that prescribers aim to rapidly correct vitamin D deficiency in pregnancy, including use of loading doses of vitamin D where clinically appropriate, but advises that factors such as severity of deficiency and patient compliance to treatment should be considered when selecting a loading dose regimen. 
  • The recommendation to seek specialist advice if loading doses are considerd clinically appropriate is pragmatic based on what CKS considers to be good clinical practice.

What lifestyle advice should I give a person with vitamin D deficiency or insufficiency?

Following treatment for vitamin D deficiency or insufficiency, provide lifestyle advice to optimize long-term levels of vitamin D.

  • Provide advice on sources of information and support, such as:
  • Provide advice on safe sun exposure to help skin synthesis of vitamin D, such as:
    • Most people can make sufficient vitamin D by going out for short periods in strong sunlight, and leaving only areas of skin that are often exposed uncovered (such as the forearms, hands, or lower legs). 
    • Longer periods of sun exposure may be needed for people with dark pigmented skin. 
    • Prolonged exposure to strong sunlight (for example, leading to burning or tanning) is unlikely to provide additional benefit, and should be avoided. 
    • Use of sunbeds should be avoided as an option for maintaining vitamin D levels as they increase the risk of developing skin cancers. 
      • The British Association of Dermatologists' Sunscreen Fact Sheet provides useful information on sunscreens and sun safety tips.
      • The Meteorological Office 'UV index' forecast indicates how strong the sun's ultraviolet (UV) rays are and when there may be an increased risk of skin burning in different parts of the UK. 
  • Provide advice on dietary sources of vitamin D.
    • Advise that it is difficult to obtain sufficient vitamin D from food sources alone. The British Dietetic Association (BDA) Vitamin D: food fact sheet may be helpful. 
    • Advise the person to continue long-term maintenance vitamin D supplementation to prevent recurrent vitamin D deficiency and to maintain bone health. See the section on How to treat for more information. 
  • Provide advice on dietary intake of calcium.
    • The British Dietetic Association (BDA) Calcium: food fact sheet may be helpful. 
    • The Royal Osteoporosis Society (ROS) Calcium-rich food chooser may be helpful. 
    • If dietary calcium intake is inadequate, advise the person to take calcium supplementation, if needed. See the section on How to treat for more information.

Basis for recommendation

These recommendations are based on the National Institute for Health and Care Excellence (NICE) guideline Sunlight exposure: risks and benefits [NICE, 2023], the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the World Health Organization (WHO) information fact sheet Ultraviolet radiation [WHO, 2022], and expert opinion in a narrative review Overview on vitamin D and sunbed use [Pierret, 2019]. 

Advising on safe sun exposure
  • The SACN publication notes that quantifying the amount of sunlight exposure that would be required during the summer to maintain a serum 25-hydroxyvitamin D greater than 25 nmol/L in 97.5% of the UK population during the following winter is not possible, due to the number and complexity of environmental and individual factors that affect endogenous vitamin D production, storage, and use [SACN, 2023]. 
  • The WHO advises that artificial tanning should never be considered as an option to achieve sufficient vitamin D status and that the use of artificial tanning devices should be avoided as they increase the risk of developing skin cancers [WHO, 2022]. 
    • Sunbeds are able to increase serum vitamin D levels, although only transiently in most cases, but where there is vitamin D deficiency or insufficiency, the current risk-benefit ratio is in favour of vitamin D supplementation instead of sunbed use. Artificial tanning devices should never be considered as an option to achieve an appropriate vitamin D status [Pierret, 2019].

How should I follow up a person with vitamin D deficiency?

  • Check the adjusted serum calcium level within 1 month after the last loading dose, or after starting lower-dose maintenance treatment with vitamin D, to detect calcium deficiency or unmasked primary hyperparathyroidism. 
    • If hypercalcaemia is detected, advise stopping vitamin D (and calcium, if taking) supplements and arrange ongoing investigation and management. See the CKS topic on Hypercalcaemia for more information.
      • People with increased sensitivity to vitamin D therapy, such as those with chronic kidney disease (CKD), sarcoidosis, tuberculosis, or hyperparathyroidism may need lower subsequent dosing. Seek specialist advice if there is any uncertainty.
    • If hypocalcaemia is detected, assess the person's dietary calcium intake and advise them to increase dietary calcium and/or on the need for calcium supplements if this is inadequate. See the section on How to treat for more information on calcium supplementation, and the section on Available preparations in Prescribing information for more detailed prescribing information.
      • If the person is already taking a calcium supplement, arrange referral to an endocrinologist for further investigation and management.
  • Routine monitoring of serum 25-hydroxyvitamin D (25[OH]D) levels is not necessary.
  • Consider checking the serum 25(OH)D level 3–6 months after starting vitamin D treatment in people:
    • With symptoms of vitamin D deficiency.
    • With a malabsorption disorder. 
    • Taking medicines that may affect the availability of vitamin D. 
    • With medical conditions that increase renal loss of vitamin D (for example, nephrotic syndrome). 
    • Where poor compliance with medication is suspected. 
    • Prescribed antiresorptive therapy who have extremely low levels of vitamin D at baseline assessment.
    • Needing sequential doses of a potent antiresorptive agent (zoledronate, denosumab, or teriparatide). 
      • If the serum 25(OH)D level is below 50 nmol/L, assess adherence to treatment and arrange referral to an appropriate specialist for investigation of an underlying cause, depending on clinical judgement.
      • If the serum 25(OH)D level is above 50 nmol/L, advise on the use of lower dose maintenance treatment with vitamin D. See the section on How to treat for more information. 
  • Advise the person to maintain adequate vitamin D levels through safe sunlight exposure and diet. See the section on Lifestyle advice for more information. 
  • If the person has ongoing symptoms despite adequate treatment with vitamin D, consider an alternative diagnosis and manage appropriately. 

Basis for recommendation

These recommendations are based on the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], an international guideline Vitamin D supplementation guidelines [Pludowski, 2018], the National Osteoporosis Guideline Group (NOGG) 2024 UK clinical guideline for the prevention and treatment of osteoporosis [NOGG, 2025], a Consensus statement on Vitamin D status assessment and supplementation: whys, whens, and hows [Giustina, 2024], and When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020], and the British National Formulary [BNF, 2026]. They are also pragmatic, based on what CKS considers good medical practice. 

Checking serum 25-hydroxyvitamin D levels
  • The recommendation that monitoring of serum 25-hydroxyvitamin D (25[OH]D) levels after a fixed loading regimen is not routinely needed is based on the Endocrine Society guideline which advises against routine testing in healthy adults [Demay, 2024]. 
  • The recommendation to consider checking 25(OH)D levels 3–6 months after starting treatment in some groups of people is based on the BNF [BNF, 2026], an international publication [Pludowski, 2018], the Endocrine Society guideline [Demay, 2024], and expert opinion in a narrative review [Pearce, 2010].
    • The international publication states that after a laboratory confirmed vitamin D deficiency the first follow-up 25(OH)D level should not be arranged before 8–12 weeks after the beginning of treatment [Pludowski, 2018]. 
    • Expert opinion in a review article notes that people with severe malabsorption or poor compliance with oral therapy may need treatment with intramuscular vitamin D [Pearce, 2010]. 
    • Testing to identify those with low 25(OH)D level, or to monitor response to therapy, may be required in special populations who are expected to require more than the dietary reference intake of vitamin D to prevent/reverse low vitamin D status, including those with malabsorption (for example, from short gut syndrome, gastric bypass, inflammatory bowel disease), those with increased vitamin D catabolism (for example, due to certain medications), and those with increased renal losses of vitamin D (for example, nephrotic syndrome) [Demay, 2024]. 
  • The recommendation to assess adherence to vitamin D therapy and arrange further investigation if there has been an inadequate response to treatment is extrapolated from expert opinion in a narrative review [Aoun, 2020].
  • Expert opinion in a review article also notes that as few adults have reversible risk factors for vitamin D deficiency, the majority of people will need lifelong vitamin D supplementation [Pearce, 2010]. 

Scenario: Prevention of vitamin D deficiency

From age 18 years onwards.

What advice should I give about prevention of vitamin D deficiency?

  • Advise the person to maintain adequate vitamin D levels through safe sunlight exposure and diet. See the section on Lifestyle advice for more information. 
  • Advise all people with risk factors for vitamin D deficiency to take a daily supplement containing 400 international units (IU, 10 micrograms equivalent) of vitamin D throughout the year. 
  • Advise all other adults (including women who are pregnant) to consider taking a daily supplement containing 400 IU of vitamin D, particularly in the autumn and winter.
    • People eligible for the NHS Healthy Start scheme can obtain free vitamin tablets (containing 400 IU of vitamin D, 400 micrograms of folic acid, and 70 mg of vitamin C). The NHS information on the Healthy Start scheme provides advice on eligibility and how to apply.
      • Most pregnancy supplements contain 400 IU of vitamin D. 
    • Advise other adults that vitamin supplement preparations containing 400 IU of vitamin D can be bought over the counter. 
    • Advise that routine monitoring of serum 25-hydroxyvitamin D (25[OH]D) levels is not needed. 
  • Assess the person's need for calcium supplementation. 
    • Assess the person's dietary calcium intake.
      • Consider using an online calcium calculator, such as the International Osteoporosis Foundation calcium calculator.
    • If the person has an inadequate calcium intake of less than 700 mg a day (or less than 1000 mg a day if the person is taking osteoporosis treatments), advise them to increase dietary calcium intake.
    • If the person is unable or unwilling to increase dietary calcium intake, consider the need for calcium supplements.
      • Advise that multivitamin preparations containing adequate daily calcium (usually 500–1200 mg) and vitamin D (400 IU) can be bought over the counter. 
      • The ROS leaflet Calcium includes a factsheet on calcium supplements and tests that may be helpful.

Basis for recommendation

The recommendations are based on the Public Health England (PHE) and National Institute for Health and Care Excellence (NICE) statement Preparing for winter: vitamin D [PHE,2020], the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the Endocrine Society guideline Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline [Demay, 2024], the Specialist Pharmacy Service (SPS) document Vitamin D deficiency: treatment during pregnancy [SPS, 2025a], the NHS England guidance Conditions for which over the counter items should not routinely be prescribed in primary care: guidance for CCGs [NHS England, 2026], and the British Dietetic Association factsheet Calcium [BDA, 2026]. 

Advising on vitamin D supplementation for adults
  • PHE and NICE advises that when outdoors during spring and summer most people make enough vitamin D, but in the UK between October and early March people don't get enough and recommends that people take a vitamin D supplement (400 IU daily) at this time of year. It also advises that some people are more at risk of not having enough vitamin D even in spring and summer, including those with dark skin (such as those with African, African-Caribbean or south Asian backgrounds), those who are not outdoors often, those in care homes, and those who cover up most of the skin when outdoors. It advises these people to take a vitamin D supplement all year round [PHE,2020].
  • The SACN publication recommends a daily reference nutrient intake (RNI) of 10 micrograms or 400 international units (IU) throughout the year for the UK population aged 4 years and above, including women who are pregnant or breastfeeding.
    • This is the average amount needed (from natural food sources, fortified foods, or supplements) by 97.5% of the population to maintain a serum 25-hydroxyvitamin D (25[OH]D) concentration at or above 25 nmol/L, when ultraviolet (UV)-B radiation exposure is minimal. It refers to average intake over a period of time (such as a week) and takes account of day-to-day variations in vitamin D intake. As a precaution, SACN recommends that the RNI is applicable throughout the year to protect population groups and unidentified people in the UK with a serum 25(OH)D concentration less than 25 nmol/L in the summer.
    • An increment to the RNI was not considered necessary for people at increased risk of vitamin D deficiency, because the recommendation for the RNI to be applicable throughout the year takes account of people with minimal sunshine exposure, including those most at risk [SACN, 2023].
  • The Endocrine Society guideline advises against empiric vitamin D supplementation (beyond the recommended dietary reference intakes [DRIs]) in the general population aged under 75 years [Demay, 2024], but does recommend supplementation for people aged 75 years and over (because of the potential to lower the risk of mortality), during pregnancy (due to the potential to lower the risk of pre-eclampsia, intra-uterine mortality, preterm birth, small-for-gestational-age birth and neonatal mortality), and in adults with high-risk prediabetes (to reduce the risk of progression to diabetes). 
    • It advises that the National Academy of Medicine DRI for people aged under 50 years to 70 years is 600 IU, and 800 IU for those aged over 70 years. 
  • Expert opinion in a review article notes that to maintain optimal vitamin D status, use of vitamin D supplementation is often needed, as sunlight exposure and dietary intake alone is usually insufficient in most people [Amrein, 2020].
  • SPS recommends that all pregnant women should take a 10 micrograms (400 units) vitamin D supplement daily from October to March, and that women with dark skin or those who cover their skin may need supplements year-round [SPS, 2025a]. 

What lifestyle advice should I give to reduce the risk of vitamin D deficiency?

Provide adults in the UK with lifestyle advice for the prevention of vitamin D deficiency.

  • Provide advice on sources of information and support, such as:
  • Provide advice on safe sun exposure to help skin synthesis of vitamin D, such as:
    • Most people can make sufficient vitamin D by going out for short periods in strong sunlight, and leaving only areas of skin that are often exposed uncovered (such as the forearms, hands, or lower legs). 
    • Longer periods of sun exposure may be needed for people with dark pigmented skin. 
    • Prolonged exposure to strong sunlight (for example, leading to burning or tanning) is unlikely to provide additional benefit, and should be avoided. 
    • Use of sunbeds should be avoided as an option for maintaining vitamin D levels as they increase the risk of developing skin cancers.  
      • The British Association of Dermatologists' Sunscreen Fact Sheet provides useful information on sunscreens and sun safety tips. 
      • The Meteorological Office 'UV index' forecast indicates how strong the sun's ultraviolet (UV) rays are and when there may be an increased risk of skin burning in different parts of the UK. 
  • Provide advice on dietary sources of vitamin D.
    • Advise that it is difficult to obtain sufficient vitamin D from food sources alone. The British Dietetic Association (BDA) Vitamin D: food fact sheet may be helpful. 
    • Advise the person to take vitamin D supplements to prevent vitamin D deficiency and to maintain bone health. See the section on Prevention for more information. 

Basis for recommendation

These recommendations are based on the National Institute for Health and Care Excellence (NICE) guideline Sunlight exposure: risks and benefits [NICE, 2023], the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the World Health Organization (WHO) information fact sheet Ultraviolet radiation [WHO, 2022], and expert opinion in a narrative review Overview on vitamin D and sunbed use [Pierret, 2019]. 

Advising on safe sun exposure
  • The SACN publication notes that recommendations on the exact amount of sunlight exposure needed for vitamin D skin synthesis are not possible [SACN, 2023]. 
    • Quantifying the amount of sunlight exposure that would be required during the summer to maintain a serum 25-hydroxyvitamin D greater than 25 nmol/L in 97.5% of the UK population during the following winter is not possible, due to the number and complexity of environmental and individual factors that affect endogenous vitamin D production, storage, and use.
  • The WHO advises that artificial tanning should never be considered as an option to achieve sufficient vitamin D status and that the use of artificial tanning devices should be avoided as they increase the risk of developing skin cancers [WHO, 2022]. 
    • Sunbeds are able to increase serum vitamin D levels, although only transiently in most cases, but where there is vitamin D deficiency or insufficiency, the current risk-benefit ratio is in favour of vitamin D supplementation instead of sunbed use. Artificial tanning devices should never be considered as an option to achieve an appropriate vitamin D status [Pierret, 2019].

Prescribing information

Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC), or the British National Formulary (BNF).

Vitamin D supplements

Available preparations

  • Vitamin D3 (colecalciferol) is the vitamin D preparation of choice for the treatment of vitamin D deficiency [Giustina, 2024].
    • For a list of medicinal forms of colecalciferol, see the British National Formulary (BNF) section on Colecalciferol.
  • Vitamin D2 (ergocalciferol) can be used in people who cannot take vitamin D3 for cultural, dietary, or religious reasons because of the animal sourcing of vitamin D, or the use of gelatine in some preparations [Demay, 2024; SPS, 2025b].
    • For a list of medicinal forms of ergocalciferol, see the BNF section on Ergocalciferol.
  • For people with specific dietary requirements, the NHS Specialist Pharmacy Service (SPS) provides guidance on prescribing vitamin D preparations for people with:
  • For those whose diet is halal or kosher, there are a variety of vitamin D supplement products available to buy online.

Loading dose regimens

  • Several vitamin D loading-dose treatment regimens are available to achieve a cumulative total of approximately 300,000 units, divided into daily or weekly doses over 6 to 10 weeks, for example:
    • 50,000 IU once weekly for 6 weeks (300,000 IU in total). 
    • 40,000 IU once weekly for 7 weeks (280,000 IU in total). 
    • 4000 IU daily for 10 weeks (280,000 IU in total).

[BNF, 2026]

Contraindications and cautions

  • Do not prescribe vitamin D to people with:
    • Hypercalcaemia or hypercalciuria — seek specialist advice.
    • Metastatic calcification. 
    • Hypervitaminosis D. 
    • Nephrolithiasis. 
    • Diseases or conditions resulting in hypercalcaemia and/or hypercalciuria. 
    • End-stage chronic kidney disease (CKD) or severe liver disease — vitamin D3 and D2 are not metabolized normally and active vitamin D metabolites may be used under specialist supervision. 
  • Prescribe vitamin D with caution to:
    • People with mild-to-moderate renal impairment. 
    • People with a co-existing condition associated with increased sensitivity to vitamin D (such as sarcoidosis, tuberculosis, lymphoma, or primary hyperparathyroidism) — seek specialist advice.
    • Pregnant women — seek specialist advice in complex cases (for example, a history of rickets in a previous pregnancy).
    • Breastfeeding women (due to the risk of infant hypercalcaemia). 

[Pludowski, 2018; Aoun, 2020; SPS, 2025a; BNF, 2026; EMC, 2026]

Adverse effects

  • Common adverse effects of vitamin D preparations include:
    • Abdominal pain, headache, nausea, and skin reactions. 
  • Uncommon adverse effects of vitamin D preparations include: 
    • Decreased appetite, arrhythmia, constipation, diarrhoea, hypertension, myalgia, thirst, vomiting, and weight loss (uncommon).
  • Vitamin D toxicity (rare) manifests mainly through hypercalcaemia and hypercalciuria, leading to soft tissue calcification, diffuse demineralization of bones, and irreversible renal and cardiovascular toxicity.
    • See the CKS topic on Hypercalcaemia for more information on the clinical presentation, investigation, and management.

[SACN, 2023; BNF, 2026]

Drug interactions

  • Potential drug interactions associated with vitamin D include: 
    • Antiepileptic drugs (carbamazepine, phenytoin, or barbiturates) — can increase the metabolism of vitamin D, leading to a reduction in the effects of vitamin D. 
      • Higher doses of vitamin D may be needed.  
    • Cardiac glycosides — may enhance the effects of digoxin and other cardiac glycosides.
      • Monitoring of ECG and calcium may be necessary. 
    • Corticosteroids — the effects of vitamin D may be reduced. 
    • Ion exchange resins (such as colestyramine) — may reduce the gastrointestinal absorption of vitamin D. 
    • Ketoconazole, miconazole, and clotrimazole — these drugs are predicted to decrease exposure to vitamin D.
      • Monitor calcium and vitamin D concentrations. 
    • Orlistat — impairs the absorption of vitamin D. 
      • Advise that vitamin D preparations should be taken at least 2 hours after taking orlistat, or at bedtime. 
    • Thiazide diuretics (such as bendroflumethiazide, indapamide, and metolazone) — increased risk of hypercalcaemia, due to reduced urinary excretion of calcium, thereby increasing the risk of hypercalcaemia. Monitor calcium concentration in people taking high doses of vitamin D regularly. 

[EMC, 2026; Preston, 2026]

Calcium supplements

Available preparations

  • There are various different calcium preparations available to prescribe, which contain different quantities of elemental calcium.
    • For a list of medicinal forms of calcium carbonate, see the British National Formulary (BNF) section on Calcium carbonate.
  • For people with specific dietary requirements, the NHS Specialist Pharmacy Service (SPS) provides guidance on prescribing calcium and vitamin D preparations for people with:

[BNF, 2026]

Contraindications and cautions

  • Do not prescribe calcium supplements to people with:
    • Conditions associated with hypercalcaemia and/or hypercalciuria (such as some forms of malignant disease). See the CKS topic on Hypercalcaemia for more information. 
  • Prescribe calcium supplements with caution to people with:
    • A history of nephrolithiasis — seek specialist advice. 
    • A co-existing condition associated with increased sensitivity to vitamin D (such as sarcoidosis, tuberculosis, lymphoma, or primary hyperparathyroidism) — seek specialist advice. 
    • Renal impairment.

[EMC, 2022; BNF, 2026]

Adverse effects

  • Common adverse effects of calcium supplements include:
    • Constipation, diarrhoea, nausea, hypercalcaemia, and hypercalciuria (uncommon).
  • Rare or very rare adverse effects of calcium supplements include:
    • Flatulence, gastrointestinal discomfort, milk-alkali syndrome, and skin reactions.
    • Milk-alkali syndrome — this may occur in calcium overdose and can cause urinary frequency, headache, loss of appetite, nausea or vomiting, tiredness or weakness, hypercalcaemia, alkalosis, and renal impairment. 

[EMC, 2022; BNF, 2026] 

Drug interactions

  • Potential drug interactions associated with calcium supplements include the following.
    • Bisphosphonates — calcium salts reduce the absorption of bisphosphonates. 
      • Bisphosphonates should be taken at least 2 hours before taking calcium supplements (this advice may vary depending on the bisphosphonate). 
    • Cardiac glycosides — calcium supplements can induce hypercalcaemia, which may enhance the effects of digoxin and other cardiac glycosides (leading to an increased risk of digitalis toxicity and serious arrhythmias).
      • Calcium level and ECG monitoring are advised. 
    • Thiazide diuretics — may reduce the urinary excretion of calcium, thereby increasing the risk of hypercalcaemia. 
      • Close monitoring (and possibly a dose reduction of calcium) is needed during concurrent use. 
    • Tetracycline antibiotics — calcium supplements may reduce the absorption of tetracyclines. 
      • Tetracyclines should be taken at least 2–3 hours before or after taking calcium supplements. 
    • Levothyroxine — calcium salts reduce the absorption of levothyroxine. 
      • Levothyroxine should be taken at least 4 hours before or after taking calcium supplements.
    • Quinolones — calcium salts may impair the absorption of quinolones (such as ciprofloxacin). 
      • Quinolone antibiotics should be taken 2 hours before or after taking calcium supplements.
    • Zinc, iron, and strontium ranelate — calcium salts reduce the absorption of zinc salts, oral iron salts, and strontium ranelate. 
      • These preparations should be taken 2 hours before or after taking calcium supplements.

[EMC, 2022; Preston, 2026]

Supporting evidence

This CKS topic is largely based on the UK Scientific Advisory Committee on Nutrition (SACN) publication Vitamin D and health [SACN, 2023], the Endocrine Society guideline Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline [Demay, 2024], National Institute for Health and Care Excellence (NICE) guideline Sunlight exposure: risks and benefits [NICE, 2023], a Consensus statement on Vitamin D status assessment and supplementation: whys, whens, and hows [Giustina, 2024], the National Osteoporosis Guideline Group (NOGG) guideline The 2024 UK clinical guideline for the prevention and treatment of osteoporosis [NOGG, 2025], the Public Health England (PHE) and National Institute for Health and Care Excellence (NICE) statement Preparing for winter: vitamin D [PHE,2020], and expert opinion in a narrative review When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update [Aoun, 2020]. The rationale for individual recommendations is outlined in the relevant basis for recommendation sections of the topic.

How this topic was developed

This section briefly describes the processes used in developing and updating this topic. Further details on the full process can be found in the About Us section and on the Clarity Informatics website.

Search strategy

A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of vitamin D deficiency in adults.

Search dates

February 2021 - September 2026

Key search terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline, limiting the search to adults.

  • exp vitamin D deficiency/ [Diagnosis, Prevention and control, therapy].
  • Vitamin d Insufficiency.kw
  • *Vitamin D
  • Cholecalciferol
  • Ergocalciferol
  • Hypovitaminosis D, Low Vitamin D

Sources of guidelines

Sources of systematic reviews and meta-analyses

  • The Cochrane Library:
    • Systematic reviews
    • Protocols
    • Database of Abstracts of Reviews of Effects
  • Medline (with systematic review filter)
  • EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

Sources of randomized controlled trials

  • The Cochrane Library:
    • Central Register of Controlled Trials
  • Medline (with randomized controlled trial filter)
  • EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

Sources of national policy

Patient experiences

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

  • Clinical accuracy.
  • Consistency with other providers of clinical knowledge for primary care.
  • Accuracy of implementation of national guidance (in particular NICE guidelines).
  • Usability.

Principles of the consultation process

  • The process is inclusive and any individual may participate.
  • To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
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  • Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
  • External reviewers are not paid for commenting on the draft topics.
  • Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
  • All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
  • All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

  • Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
  • Stakeholders identified from the following groups are invited to review draft topics:
    • Experts in the topic area.
    • Professional organizations and societies (for example, Royal Colleges).
    • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
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Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

  • Topic selection
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  • First draft internal review
  • Second draft internal review
  • External review
  • Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

  • Animal studies
  • Original research is not written in English

Possible exclusions for reviewed literature:

  • Sample size too small or study underpowered
  • Bias evident or promotional literature
  • Population not relevant
  • Intervention/treatment not relevant
  • Outcomes not relevant
  • Outcomes have no clear evidence of clinical effectiveness
  • Setting not relevant
  • Not relevant to UK
  • Incorrect study type
  • Review article
  • Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

  • Feasibility
    • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
  • Organizational and Financial Impact Analysis
  • Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
    • Eligible population
    • Current interventions
    • Likely uptake of new intervention or recommendation
    • Cost of the current or new intervention mix
    • Impact on other costs
    • Condition-related costs
    • In-direct costs and service impacts
    • Time dependencies
  • Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

  • Personal financial interests
  • Personal family interest
  • Personal non-financial interest
  • Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.

References

  • ACOG (2011) Vitamin D: screening and supplementation during pregnancy. American College of Obstetrics and Gynecologists. [Free Full-text]
  • Amrein, K., Scherkl, M., Hoffmann, M., et al. (2020) Vitamin D deficiency 2.0: an update on the current status worldwide. European Journal of Clinical Nutrition 74(11), 1498-1513. [Abstract] [Free Full-text]
  • Aoun, A., Maalouf, J., Fahed, M., et al. (2020) When and how to diagnose and treat vitamin D deficiency in adults: a practical and clinical update. Journal of Dietary Supplements 17(3), 336-354. [Abstract]
  • Avenell, A., Bolland, M.J. and Grey, A. (2021) Population vitamin D supplementation in UK adults: too much of nothing? Drug and Therapeutics Bulletin 59(1), 7-12. [Abstract]
  • BDA (2026) Calcium. British Dietetic Association. [Free Full-text]
  • BNF (2026) British National Formulary. National Institute for Health and Care Excellence. https://bnf.nice.org.uk [Free Full-text]
  • Bolland, M.J., Avenell, A., Smith, K., et al. (2021) Vitamin D supplementation and testing in the UK: costly but ineffective? BMJ 372. [Abstract]
  • Cashman, K.D., Dowling, K.G., Skrabakova, Z., et al. (2016) Vitamin D deficiency in Europe: pandemic? The American Journal of Clinical Nutrition 103(4), 1033-1044. [Abstract] [Free Full-text]
  • Crowe, F.L., Jolly, K., MacArthur, C., et al. (2019) Trends in the incidence of testing for vitamin D deficiency in primary care in the UK: a retrospective analysis of The Health Improvement Network (THIN), 2005-2015. BMJ Open 9(6). [Free Full-text]
  • Demay, M.B., Pittas, A.G., Bikle, D.D. et al. (2024) Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism 109(8), 1907-1947. [Abstract]
  • EMC (2022) SPC for Calcichew 500mg Chewable Tablets. Electronic Medicines Compendium. Datapharm Communications Ltd. https://www.medicines.org.uk/emc [Free Full-text]
  • EMC (2026) SPC for Strivit D3 800 IU Capsules, Soft. Electronic Medicines Compendium. Datapharm Communications Ltd. https://www.medicines.org.uk/emc [Free Full-text]
  • Giustina, A., Bilezikian, J.P.,  Adler, R.A. et al. (2024) Consensus statement on Vitamin D status assessment and supplementation: whys, whens, and hows. Endocrine Reviews 45(5), 625-654. [Abstract]
  • Holick, M.F. (2017) The vitamin D deficiency pandemic: approaches for diagnosis, treatment and prevention. Reviews in Endocrine and Metabolic Disorders 18(2), 153-165. [Abstract]
  • LeFevre, M.L. LeFevre, M.N. (2018) Vitamin D screening and supplementation in community-dwelling adults: common questions and answers. American Family Physician 97(4), 254-260. [Abstract] [Free Full-text]
  • NHS England (2026) Conditions for which over the counter items should not be routinely prescribed in primary care. NHS England. https://www.england.nhs.uk [Free Full-text]
  • NICE (2019) Hyperparathyroidism (primary): diagnosis, assessment and initial management. National Institute for Health and Care Excellence. http://www.nice.org.uk [Free Full-text]
  • NICE (2023) Sunlight exposure: risks and benefits. National Institute for Health and Care Excellence. https://www.nice.org.uk [Free Full-text]
  • NICE (2026) Suspected cancer: recognition and referral. National Institute for Health and Care Excellence. https://www.nice.org.uk [Free Full-text]
  • NOGG (2025) The 2024 UK clinical guideline for the prevention and treatment of osteoporosis. Archives of Osteoporosis 20(1), 119. [Abstract] [Free Full-text]
  • OHID (2025) National diet and nutrition survey 2019 to 2023: report. Office for Health Improvement and Disparities. https://www.gov.uk [Free Full-text]
  • Pearce, S.H.S. and Cheetham, T.D. (2010) Diagnosis and management of vitamin D deficiency. BMJ 340, b5664.
  • PHE (2020) Statement from PHE and NICE on vitamin D supplementation during winter. Public Health England. https://www.gov.uk [Free Full-text]
  • Pierret, L., Suppa, M., Gandini, S. et al. (2019) Overview on vitamin D and sunbed use. Journal of the European Academy of Dermatology and Venereology 33(Suppl 2), 28-33. [Abstract]
  • Pludowski, P., Holick, M.F., Grant, W.B., et al. (2018) Vitamin D supplementation guidelines. Journal of Steroid Biochemistry and Molecular Biology 175, 125-135. [Abstract]
  • Preston, C.L. (2026) Stockley's Drug Interactions. Medicines Complete. Pharmaceutical press. https://www.medicinescomplete.com
  • SACN (2023) Vitamin D and Health. Scientific Advisory Committee on Nutrition. https://www.gov.uk [Free Full-text]
  • SPS (2025a) Vitamin D deficiency: treatment during pregnancy. Specialist Pharmacy Service. [Free Full-text]
  • SPS (2025b) Choosing vitamin D products for vegetarians or vegans. Specialist Pharmacy Service. [Free Full-text]
  • UKTIS (2026) Use of vitamin D in pregnancy. UK Teratology Information Service. [Free Full-text]
  • WHO (2022) Ultraviolet radiation. Ultraviolet radiation. World Health Organization. [Free Full-text]
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