Previous changes

May 2024 — minor update. Information added stating that concomitant treatment with clarithromycin and ivabradine is now contraindicated and caution is now advised when co-administering clarithromycin with edoxaban, as per the manufacturer's updated SPC.

March 2024 — minor update. Information that people with confirmed cryptosporidiosis or giardiasis should not go swimming for 2 weeks after the last episode of diarrhoea has also been added to the sections on management of confirmed causes.

November 2023 — minor update. The recommendation to prescribe tinidazole for treatment of giardiasis and the prescribing information have been removed from this topic as the product has been discontinued in the UK, and replaced with a recommendation to prescribe metronidazole as well as appropriate prescribing information. 

July 2023 — minor update. The summary of manufacturer’s product characteristics for clarithromycin was updated to include a warning regarding concomitant treatment with domperidone (due to the risk of QT prolongation and cardiac arrhythmias).

June 2023 — minor update. A recommendation to ask about sexual history, particularly in men who have sex with men, has been added to this topic in line with the British Association of Sexual Health and HIV (BASHH) United Kingdom national guideline for the management of sexually transmitted enteric infections 2023.

June 2022 — minor update. Minor typographical error corrected and the information on clarithromycin interactions in the prescribing information section has been consolidated and updated.

July to August 2020 — reviewed. A literature search was conducted in July 2020 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of the topic. The topic has undergone major restructuring, with several nodes merged to improve clarity and navigation. The node on Prevalence has been deleted and the content incorporated into the Causes section. The Scenario: Child - remote presentation has been deleted, and the content incorporated into the Scenario: Child. The sections on diagnosis and management have been updated in line with Public Health England (PHE) and other current literature. The Prescribing information section has been updated with currently recommended drugs to prescribe in primary care for acute gastroenteritis owing to specific causes.

March 2019 — minor update. Prescribing information for quinolones has been updated in line with the Medicines and Healthcare products Regulatory Agency (MHRA) publication Fluoroquinolone antibiotics: new restrictions and precautions for use due to very rare reports of disabling and potentially long-lasting or irreversible side effects (2019).

January 2019 — minor update. Aortic aneurysm and dissection is now listed as an adverse effect of ciprofloxacin in the section on Prescribing information. 

October 2018 — minor update. Adverse effects of metronidazole updated in the Prescribing information section.

September 2017 — minor update. Text update on quinolones according to the manufacturers' Summary of Product Characteristics (SPC), to align all CKS topics advice on prescribing. 

November 2016 — minor update. The adverse effects of loperamide have been updated to include information in a US Food and Drug Administration (FDA) 2016 drug safety communication, warning that exceeding the maximum dose can cause serious cardiac problems including QT interval prolongation, Torsades de Pointes or other ventricular arrhythmias, syncope, and cardiac arrest.

July 2015 — minor update. Information on the concurrent use of clarithromycin or erythromycin with statins has been clarified.

August 2014 — reviewed. A literature search was conducted in July 2014 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials (RCTs) published since the last revision of the topic. No major changes to clinical recommendations have been made. However, some sections have been reworded for clarity, and overview sections have been added in each scenario.

February 2013 — minor update. The 2013 QIPP options for local implementation have been added to this topic.

October 2012 — minor update. The 2012 QIPP options for local implementation have been added to this topic.

August 2011 — minor update. Text changed to include advice on the management of acute bloody diarrhoea potentially caused by vero cytotoxin-producing Escherichia coli in children. Several minor typographical errors corrected. Issued in September 2011.

May 2011 — minor update. The 2010/2011 QIPP options for local implementation have been added to this topic. Issued in June 2011.

March 2011 — topic structure revised to ensure consistency across CKS topics. No changes to clinical recommendations have been made.

August 2010 — minor update. Following a recent outbreak of Escherichia coli 0157 at an open farm in the UK, the Health Protection Agency (HPA) has reminded prescribers that children with bloody diarrhoea should be admitted to hospital, to confirm the diagnosis and prevent the spread of infection to others in the household. Issued in August 2010.

April 2010 — minor update. New notifiable diseases advice has been issued by the Department of Health. Issued in April 2010.

July to September 2009 — converted from CKS guidance to CKS topic structure. The evidence-base has been reviewed in detail, and recommendations are more clearly justified and transparently linked to the supporting evidence. The information on prevention of travellers' diarrhoea and management of a person with Clostridium difficile infection are now in separate CKS topics. Together with the updated CKS topics on Diarrhoea - antibiotic associated and Diarrhoea - prevention and advice for travellers, this CKS topic replaces the former topic on Gastroenteritis.

November 2008 — minor update to the text regarding the assessment and investigation of pregnant women with gastroenteritis. Issued in December 2008.

July to September 2006 — reviewed. Validated in December 2006 and issued in January 2007.

July 2007 — minor update to the text to include advice regarding the assessment and investigation of pregnant women with gastroenteritis.

January 2006 — minor update. Nalidixic acid tablets discontinued and prescriptions have been removed. Issued in February 2006.

June 2003 — reviewed. Validated in September 2003 and issued in October 2003.

January 2000 — rewritten. Validated in March 2000 and issued in May 2000.

October 1998 — written.

New evidence

Evidence-based guidelines

No new evidence-based guidelines since 1 June 2026.

HTAs (Health Technology Assessments)

No new HTAs since 1 June 2026.

Economic appraisals

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

Systematic reviews and meta-analyses

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

Primary evidence

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

New policies

No new national policies or guidelines since 1 June 2026.

New safety alerts

No new safety alerts since 1 June 2026.

Changes in product availability

No changes in product availability since 1 June 2026.

Viruses

• Rotavirus
  • This is the most common cause of viral gastroenteritis in children, however, there has been a reduction in disease prevalence since the introduction of the rotavirus vaccine, as part of the UK national childhood immunization programme. See the CKS topic on Immunizations - childhood for more information.
  • Most cases are transmitted by person-to-person spread by the faecal-oral route, or more rarely by contact with contaminated surfaces. Most cases in the UK occur in winter and spring.
  • Symptoms include watery diarrhoea and vomiting with or without fever and abdominal pain. Vomiting usually settles within 1–3 days, and diarrhoea within 5–7 days, but can persist for 2 weeks.
  • Infection in adults is uncommon because immunity is long-lasting.
• Noroviruses (formerly known as 'Norwalk-like viruses')
  • Norovirus is the commonest cause of gastroenteritis in England and Wales, with an increased prevalence during colder months.
  • Infection can occur in people of all ages because immunity is not long-lasting.
  • Symptoms begin 24–48 hours after infection and last for 12–60 hours. Sudden-onset nausea is followed by projectile vomiting and watery diarrhoea. There may be associated fever, headache, abdominal pain, and myalgia. Most people make a full recovery within 1–2 days.
  • Transmission is person-to-person, usually by the faecal-oral route. It can also be transmitted by consumption of contaminated food (such as oysters) or water, or contact with contaminated surfaces (such as toilets, soft furnishings, or floors), and outbreaks are common in semi-closed environments such as schools, hospitals, care homes, and cruise ships.
• Adenoviruses
  • These commonly cause respiratory tract infections, but can also cause gastroenteritis, particularly in children.

[PHE, 2020]

Bacteria

• Campylobacter jejuni and Campylobacter coli
  • These are the most commonly reported bacterial causes of infectious intestinal disease in England and Wales and are among the commonest causes of travellers' diarrhoea in the UK.
  • Infection may be asymptomatic in 25–50% of people or cause diarrhoea (which may be bloody), nausea, vomiting, abdominal cramps, and fever.
  • Most cases are self-limiting within 2–3 days and usually resolve within 1 week.
  • It is usually associated with the consumption of contaminated food and drink, such as undercooked meat (especially poultry), unpasteurised milk, or untreated water, but the source of infection is often not found.
• Escherichia coli (including Shiga toxin-producing E. coli [STEC] or verocytotoxin-producing E. coli [VTEC])
  • E. coli O157 is the most common serogroup of STEC, causing infections in the UK.
  • In England and Wales, rates of infection are highest in children under 5 years of age, with the peak incidence in children aged 1–4 years.
  • Infection with E. coli O157:H7 may be asymptomatic or cause diarrhoea (which may be bloody), fever, abdominal cramps, and vomiting. Illness is usually self-limiting and resolves within 10 days.
  • E. coli is transmitted through contaminated food, particularly meat, salad products, water, and unpasteurised milk. It can also be transmitted person-to-person by direct contact (faecal-oral route), particularly in households, schools and childcare settings, and care homes; by contact with infected animals (especially cattle, sheep, goats, and other ruminants); or environmental exposure to contaminated water.
• Salmonellosis (excluding Salmonella typhi and Salmonella paratyphi causing enteric fever)
  • The majority of cases are sporadic, but outbreaks may occur in the general population and in institutions.
  • Ingestion of contaminated food is the most common source, such as red and white meats, raw eggs, milk, and dairy products. Person-to-person spread, and contact with infected animals can also occur.
  • Typical features are watery and sometimes bloody diarrhoea, abdominal pain, headache, nausea, vomiting, and fever. The illness usually lasts for 4–7 days, and people usually recover spontaneously.
• Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei
  • Shigellosis is most commonly transmitted person-to-person by the faecal-oral route, particularly in households, nurseries, and schools. More rarely, it can be transmitted through contaminated food or sexually transmitted (particularly in men who have sex with men).
  • Shigellosis occurs most commonly in children less than 5 years of age, but infection can occur in all ages. Infections peak in late summer in the UK.
  • Typically, 1–3 days after infection, there is diarrhoea (may have blood and mucus), fever, and abdominal cramps, with or without nausea and vomiting, headache, and malaise. Shigellosis usually resolves in 5–7 days.
• Yersinia enterocolitica 
  • This is a rare infection and occurs most commonly in children.
  • Common symptoms include watery diarrhoea (often bloody), fever, and abdominal pain. In older children and adults, right-sided abdominal pain and fever may occur.
  • Symptoms typically develop 4–7 days after exposure and may last 2 days to 6 weeks.
  • Y. enterocolitica is transmitted by direct contact with infected animals and person-to-person (faecal-oral route), and through contaminated food (especially raw pork and pork products) and water.

[PHE, 2020]

Parasites

• Cryptosporidiosis
  • Cryptosporidium is one of the most common protozoal causes of gastroenteritis in the UK, and about 20% of cases are associated with recent foreign travel.
  • Infection is transmitted by animal-to-human or human-to-human contact, by occupational or recreational exposure to contaminated land or water, or by consuming contaminated water or food.
  • It typically causes profuse watery diarrhoea associated with abdominal cramps or pain, nausea, vomiting, fever, and loss of appetite. Symptoms usually last for 1–2 weeks, and recurrence of symptoms is reported in around one-third of cases.
• Entamoeba histolytica (amoebiasis)
  • Transmission occurs through the ingestion of contaminated food or water. Person-to-person transmission may also occur between household and sexual contacts via the faecal-oral route.
  • Most cases in the UK are imported by travellers to endemic areas.
  • 90% of cases are asymptomatic. Diarrhoea with or without dysentery occurs in intestinal disease.
  • Symptoms are often mild diarrhoea and abdominal pain, but severe disease (amoebic dysentery) can occur, causing fever, severe abdominal pain, and blood and mucus in the faeces.
• Giardia intestinalis or Giardia lamblia
  • Giardiasis can be transmitted by person-to-person spread by the faecal-oral route; by contact with the faeces of infected animals; by consumption of contaminated food or drink; waterborne, including swimming in contaminated water; or by sexual transmission, particularly among men who have sex with men. Many cases are associated with recent foreign travel, particularly from South Asia, and it is the most commonly identified pathogen in returning travellers with prolonged diarrhoea.
  • Symptoms include diarrhoea, malaise, abdominal pain, loss of appetite, flatulence, bloating, and rarely nausea. Malabsorption, weight loss, and faltering growth may occur in children. See the CKS topic on Faltering growth for more information.

[Barrett, 2016; PHE, 2020]

Basis for recommendation

The recommendations on diagnosis are based on the National Institute for Health and Care Excellence (NICE) clinical guideline Diarrhoea and vomiting caused by gastroenteritis: diagnosis, assessment, and management in children younger than 5 years [NICE, 2022], the Public Health England (PHE) publication Recommendations for the public health management of gastrointestinal infections 2019. Principles and practice [PHE, 2020], the joint European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN)/European Society for Pediatric Infectious Diseases (ESPID) publication Evidence-based guidelines for the management of acute gastroenteritis in children in Europe: update 2014 [Guarino, 2014], and expert opinion in narrative reviews [Ferris, 2023].

Assessing for dehydration in children

Be aware that risk factors for developing dehydration in children include [NICE, 2022]:

• Infants younger than 1 year of age, particularly younger than 6 months.
• Infants who were of low birthweight.
• Children who have passed six or more diarrhoeal stools in the previous 24 hours.
• Children who have vomited three or more times in the previous 24 hours.
• Children who have not been offered, or have not been able to tolerate, supplementary fluids before presentation.
• Infants who have stopped breastfeeding during the illness.
• Children with signs of malnutrition.

Table 1. Symptoms and signs of dehydration and shock.

Assessing for dehydration in adults

 Assess whether the patient is hypovolaemic. Indicators that a patient may need urgent fluid resuscitation include [NICE, 2017]:

• Systolic blood pressure is less than 100 mmHg.
• Heart rate is more than 90 beats per minute.
• Capillary refill time is more than 2 seconds, or peripheries are cold to the touch.
• Respiratory rate is more than 20 breaths per minute.
• National Early Warning Score (NEWS) is 5 or more.
• Passive leg raising suggests fluid responsiveness.
  • Passive leg raising is a bedside method to assess fluid responsiveness in a patient. It is best undertaken with the patient initially semi-recumbent and then tilting the entire bed through 45°. Alternatively, it can be done by lying the patient flat and passively raising their legs to greater than 45°. If, at 30 to 90 seconds, the patient shows signs of haemodynamic improvement, it indicates that volume replacement may be required. If the condition of the person deteriorates, in particular, breathlessness, it indicates that the patient may be fluid overloaded.

Basis for recommendation

The recommendations on assessment are largely based on the National Institute for Health and Care Excellence (NICE) clinical guideline Diarrhoea and vomiting caused by gastroenteritis: diagnosis, assessment, and management in children younger than 5 years [NICE, 2022]; Recommendations for the public health management of gastrointestinal infections 2019. Principles and practice [PHE, 2020], and UK Standards for microbiology investigations: Gastroenteritis [UKHSA, 2026a]; the joint European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN)/European Society for Pediatric Infectious Diseases (ESPID) publication Evidence-based guidelines for the management of acute gastroenteritis in children in Europe: update 2014 [Guarino, 2014]; the Infectious Diseases Society of America (IDSA) publication Clinical practice guidelines for the diagnosis and management of infectious diarrhea [Shane, 2017]; the American College of Gastroenterology (ACG) clinical guideline Diagnosis, treatment, and prevention of acute diarrheal infections in adults [Riddle et al, 2016]; the World Gastroenterology Organisation (WGO) global guidelines Acute diarrhea in adults and children: a global perspective [World Gastroenterology Organisation, 2012]; the expert consensus publication Guidelines for the prevention and treatment of travelers' diarrhea: a graded expert panel report [Riddle, 2017]; and expert opinion in review articles on acute diarrhoea in adults [Jones, 2009], on gastroenteritis in children [Hartman, 2019; Florez, 2020], on viral gastroenteritis [Banyai, 2018], and on travellers' diarrhoea [Steffen, 2015; Barrett, 2016].

Clinical features on history taking

• These recommendations are based on the NICE clinical guideline [NICE, 2022], a PHE publication [PHE, 2020], the ESPGHAN/ESPID joint publication [Guarino, 2014], the IDSA publication [Shane, 2017], the WGO expert consensus guidelines [World Gastroenterology Organisation, 2012], and expert opinion in review articles [Jones, 2009; Hartman, 2019; Florez, 2020].
  • Taking a full history can help distinguish between infectious and non-infectious causes of diarrhoea [Jones, 2009].
  • Approximately 40% of people with Campylobacter spp. infection have bloody diarrhoea, compared with 10% of people with infections owing to other causes. Bloody diarrhoea is also common in infection with Shiga toxin-producing Escherichia coli (STEC), Salmonella spp., Shigella spp., and Yersinia spp. infection [Jones, 2009].
  • Fever is present in about 50% of people with infective diarrhoea, particularly Campylobacter spp. and rotavirus infections, compared with about 10% in non-infective diarrhoea [Jones, 2009].
  • Taking a history of comorbidities and/or immunosuppression is important as these people may have a more severe and prolonged course of infection (for example with rotavirus or norovirus), or may be at increased risk for contracting opportunistic infections (such as Clostridium difficile, Cryptosporidium spp., and Giardia spp.) [Guarino, 2014].
  • Taking a travel history is important, as at least 50% of travellers returning from non-European destinations, particularly Central America, South America, and South Asia, are likely to have a bacterial or parasitic cause for their diarrhoea [Jones, 2009].

Clinical features on examination

• The recommendations on assessing for clinical features of dehydration and shock are based on the NICE clinical guideline [NICE, 2022], the ESPGHAN/ESPID joint publication [Guarino, 2014], the WGO expert consensus guidelines [World Gastroenterology Organisation, 2012], and expert opinion in a review article [Hartman, 2019].
  • The ESPGHAN/ESPID publication notes that the three best individual signs for assessment of dehydration in children are prolonged capillary refill time, abnormal skin turgor, and abnormal respiratory pattern.

Basis for recommendation

The information on differential diagnosis is largely based on the National Institute for Health and Care Excellence (NICE) clinical guideline Diarrhoea and vomiting caused by gastroenteritis: diagnosis, assessment, and management in children younger than 5 years [NICE, 2022], the Infectious Diseases Society of America (IDSA) publication Clinical practice guidelines for the diagnosis and management of infectious diarrhea [Shane, 2017], the World Gastroenterology Organisation global guidelines Acute diarrhea in adults and children: a global perspective [World Gastroenterology Organisation, 2012], and expert opinion in a review article on acute diarrhoea in adults [Jones, 2009], on gastroenteritis in children [Hartman, 2019], and on travellers' diarrhoea [Barrett, 2016]. It is also pragmatic, based on what CKS considers to be good clinical practice.

Basis for recommendation

Arranging stool culture and sensitivity testing

• The recommendations on when to arrange stool testing are based on the NICE clinical guideline [NICE, 2022], the UKHSA publications [UKHSA, 2026a; PHE, 2020], the ESPGHAN/ESPID joint publication [Guarino, 2014], the WGO expert consensus guidelines [World Gastroenterology Organisation, 2012], the ACG clinical guideline [Riddle et al, 2016], the IDSA publication [Shane, 2017], guidelines on travellers' diarrhoea [Riddle, 2017], and expert opinion in review articles [Steffen, 2015; Banyai, 2018; Hartman, 2019; Florez, 2020].
  • The information that stool tests are not routinely needed is based on the NICE clinical guideline, which states that most cases in children are due to viral gastroenteritis, and most children do not need antibiotic treatment if there is a bacterial cause found. This approach is supported by expert opinion in a review article, which notes that most episodes of infective diarrhoea in children are self-limiting, and identification of a pathogen does not affect the management or natural history of the disease [Florez, 2020].
  • The recommendation about people with severe symptoms or who are immunocompromised is extrapolated from the NICE clinical guideline and expert opinion in a review article [Banyai, 2018].
  • The recommendation about suspected dysentery is based on the NICE clinical guideline, the ESPGHAN/ESPID publication, the WGO expert consensus guidelines, the IDSA publication, and expert opinion in a review article [Banyai, 2018].
  • The recommendation about suspected Clostridium difficile infection is based on the UKHSA publication [UKHSA, 2026a].
  • The recommendation about diarrhoea persisting after 7 days is extrapolated from the NICE clinical guideline, the ACG clinical guideline on adults, and expert opinion in a review article [Jones, 2009].
  • The recommendation about suspected food poisoning is based on the PHE publication [UKHSA, 2026a].
  • The recommendation about recent travel to at-risk areas is based on the NICE clinical guideline, the UKHSA publication [UKHSA, 2026a], the ESPGHAN/ESPID publication, guidelines on travellers' diarrhoea [Riddle, 2017], and expert opinion in review articles [Barrett, 2016; Banyai, 2018].
  • The recommendation about recurrent or prolonged diarrhoea is based on the WGO expert consensus guidelines, the IDSA publication, and expert opinion in a review article [Steffen, 2015].
  • The information on sending three specimens for ova, cysts, and parasites is based on the the UKHSA publication [UKHSA, 2026a].
  • The recommendations on people at risk of transmission are based on the PHE publication [PHE, 2020].
  • The recommendation about testing if there is diagnostic uncertainty is based on the NICE clinical guideline, which notes that other non-enteric infections, non-infective gastrointestinal disorders, or some drugs may cause similar symptoms.
  • The recommendation about testing if there has been contact with a case in specific situations is based on the PHE publication [PHE, 2020].
  • The recommendation to seek specialist advice if there is uncertainty about the need for testing is extrapolated from the PHE publication [PHE, 2020], and is also pragmatic, based on what CKS considers to be good clinical practice.

Not arranging blood tests for acute gastroenteritis in primary care

• This recommendation is extrapolated from the NICE clinical guideline [NICE, 2022] and the ESPGHAN/ESPID joint publication [Guarino, 2014], which notes that investigations including serum electrolytes are not usually necessary for cases of acute gastroenteritis with mild-to-moderate dehydration.

When should I admit a child with gastroenteritis?

If a child presents with suspected gastroenteritis:

• Arrange emergency hospital admission if:
  • The child is systemically unwell and/or there are clinical features suggesting severe dehydration and/or progression to shock.
  • There is intractable or bilious vomiting.
  • There is acute-onset painful, bloody diarrhoea in previously healthy children, or confirmed Shiga toxin-producing Escherichia coli (STEC) infection 0157.
  • There is a suspected serious complication, such as haemolytic uraemic syndrome or sepsis.
• Consider arranging hospital assessment, the urgency depending on clinical judgement, if:
  • There are clinical features suggesting a potentially life-threatening or serious alternative diagnosis.
  • There is an inadequate response to oral rehydration salt (ORS) solution, or the child is unable to take ORS solution orally.
  • There are red flag symptoms or signs suggesting increased risk of progression to shock, and the child is clinically deteriorating despite use of ORS solution.
  • There are risk factors for developing dehydration.
•  
• The parents/carers are unable to monitor the child's condition or provide appropriate management safely at home.
• Liaise with a microbiologist or consultant in communicable disease control if:
  • There is uncertainty about the need for admission in a child with a confirmed microbiological cause on stool culture and sensitivity testing.
  • There is uncertainty about the need for management in a child with moderate or severe suspected travellers' diarrhoea.

How should I manage a child with gastroenteritis in primary care?

If a child does not need immediate hospital admission, advise on management and follow up in primary care:

• Provide advice on sources of information and support, such as:
  • The NHS leaflets Diarrhoea and vomiting and Food poisoning.
• Advise on how to monitor fluid intake and prevent/treat dehydration.
  • In children without clinical features of dehydration, advise the parents/carers to:
    • Continue with usual feeds, including breastfeeding (if applicable) and other milk feeds.
    • Encourage regular fluid intake.
    • Offer low-osmolarity oral rehydration salt (ORS) solution as supplemental fluid if the child is at increased risk of dehydration.
    • Discourage fruit juices and carbonated drinks, especially in children at increased risk of dehydration.
  • In children with clinical features of dehydration who can safely be managed at home, advise the parents/carers to:
    • Give the child low-osmolarity ORS solution frequently and in small amounts to rehydrate.
    • Consider supplementation with usual fluids if the child refuses to take sufficient quantities of ORS solution, provided there are no red flag symptoms and signs (suggesting increased risk of progression to shock).
    • Discourage fruit juices and carbonated drinks.
    • Avoid giving solid food until the child is rehydrated.
  • After rehydration, advise the parents/carers to:
    • Encourage the child to drink plenty of usual fluids, including milk feeds (if these were stopped).
    • Reintroduce the child's usual diet.
    • Discourage fruit juices and carbonated drinks until the diarrhoea has stopped.
• Advise that drug treatment with antidiarrhoeal drugs, antiemetics, zinc supplements, and probiotics is not recommended for use in children in primary care.
• Do not routinely prescribe antibiotics to children with gastroenteritis.
  • Arrange treatment of confirmed microbial pathogens, if appropriate, following stool culture and sensitivity testing. See the section on Management of confirmed cause for more information.
• Advise on methods to prevent transmission of infection:
  • Wash hands thoroughly with liquid soap in warm running water, and dry carefully.
  • Always use a flush toilet, if possible.
    • If a potty must be used, it should be handled with gloves, the contents disposed of into the toilet, and then washed with hot water and detergent and allowed to dry.
    • Wash hands after going to the toilet and changing nappies; before preparing, serving, or eating food; and after handling pets or non-domestic animals.
    • Toilet seats, flush handles, wash-hand basin taps, surfaces, and toilet door handles should be cleaned at least once daily with hot water and detergent. A disinfectant and disposable cloth (or one dedicated for toilet use) should be used to clean toilets.
  • Do not share towels/flannels and bathwater used by infected children.
  • Wash soiled clothing and bed linen separately from other clothes and at a high temperature (for example, 60°C or higher for cotton), after removal of excess faecal matter or vomitus into the toilet. Soaking in disinfectant is not necessary. The washing machine should not be more than half full to allow for adequate washing and rinsing.
  • The Public Health England (PHE) leaflet Minimising the spread of gastrointestinal infection provides detailed information on personal hygiene, environmental cleaning, and disposal of soiled materials.
• Advise that children should not attend school or other childcare/social settings until at least 48 hours after the last episode of diarrhoea or vomiting.
  • See the PHE publication Health protection in children and young people's settings, including education for more information.
  • Note: for some gastrointestinal infections, longer periods of exclusion are needed, and 'microbiological clearance' with negative stool testing may be required before return to specific settings. See the section on Management of confirmed cause for more information.
  • Note: if cryptosporidiosis or giardiasis is suspected or confirmed, children should not go swimming for 2 weeks after the last episode of diarrhoea.
• Advise parents/carers on the need for follow up and to seek urgent medical advice if a child has:
  • Any features requiring hospital admission or assessment. See the section on Hospital admission for more information.
  • Any new features requiring stool culture testing, such as blood, mucus, and/or pus in the stool (suggesting possible dysentery).
  • Symptoms that do not resolve within the expected timeframe — arrange stool culture testing and consider whether an alternative diagnosis is possible.
    • Diarrhoea usually lasts 5–7 days, and in most children stops within 2 weeks.
    • Vomiting usually lasts 1–2 days, and in most children stops within 3 days.
• Notify the local health protection team immediately by completing a notification form, if any of the following notifiable diseases or organisms are suspected:
  • Food poisoning (such as suspected Bacillus cereus, Campylobacter spp., Clostridium perfringens, Cryptosporidium spp., Entamoeba histolytica, verocytotoxigenic Escherichia coli [including E. coli O157:H7], Salmonella spp., Giardia lamblia, and Yersinia pestis), including suspected clusters or outbreaks.
  • Haemolytic uraemic syndrome.
  • Infectious bloody diarrhoea, such as Shigella spp.
  • Enteric fever (typhoid or paratyphoid fever).
  • Cholera.

How should I manage gastroenteritis due to a confirmed microbiological cause?

If a child with gastroenteritis has a specific microbiological cause confirmed after stool culture and sensitivity testing:

• Seek advice from the local health protection team regarding the need for antibiotic treatment or stool testing for microbiological clearance, particularly in a child:
  • Younger than 6 months of age with salmonella infection, or who is malnourished or immunocompromised with salmonella infection.
  • With Shiga toxin-producing Escherichia coli (STEC) infection.
    • There is no effective antibiotic treatment available for STEC infection, and advise not to give antibiotic treatment.
    • Specialist advice is needed regarding monitoring for the complication of haemolytic uraemic syndrome.
    • Specialist advice is also needed regarding stool testing for microbiological clearance in children at increased risk of transmission of infection — two consecutive negative stool samples are usually needed, taken at least 24 hours apart, once the child is symptom-free for at least 48 hours, before the child can return to school or other childcare settings.
  • With giardiasis.
    • Drug treatment with metronidazole may be recommended following specialist advice.
    • Advise the person that they should not go swimming for 2 weeks after the last episode of diarrhoea.
  • With dysenteric shigellosis.
    • Antibiotic treatment is not usually needed for children with mild symptoms of shigellosis, but if symptoms are severe (high fever, bloody and/or high-output diarrhoea) or the child is immunocompromised, seek specialist advice on the need for antibiotic treatment.
    • Specialist advice is needed regarding exclusion of cases from childcare settings, and the need for microbiological clearance stool testing, which varies depending on the Shigella species.
  • With dysenteric amoebiasis.
    • Drug treatment is usually recommended for all confirmed cases after specialist advice.
    • Specialist advice is needed regarding the need for microbiological clearance to confirm treatment success, 1 week after completing treatment.
  • With campylobacteriosis.
    • Antibiotic treatment is not usually needed for children with mild symptoms, as infection is usually self-limiting.
    • If symptoms are severe (high fever, bloody and/or high-output diarrhoea), the child is immunocompromised, or symptoms are worsening, seek specialist advice regarding the need for antibiotic treatment.
  • With cryptosporidiosis.
    • There is no specific treatment licensed in the UK.
    • Advise the person that they should not go swimming for 2 weeks after the last episode of diarrhoea.
    • Seek specialist advice if the child is severely immunocompromised, owing to the risk of serious and life-threatening complications.

When should I admit an adult with gastroenteritis?

If an adult presents with suspected gastroenteritis:

• Arrange emergency hospital admission if:
  • The person is systemically unwell and/or there are clinical features suggesting severe dehydration and/or progression to shock.
  • There is intractable vomiting or high-output diarrhoea.
  • There is a suspected serious complication, such as sepsis.
• Consider arranging hospital assessment, the urgency depending on clinical judgement, if:
  • There are clinical features suggesting a potentially life-threatening or serious alternative diagnosis.
  • There is an inadequate response to oral rehydration salt (ORS) solution, the person is unable to take ORS solution orally, or they are clinically deteriorating.
  • There are risk factors for developing dehydration, such as in the elderly, immunocompromised, those with co-morbid conditions or concurrent illness.
  • The person/carers are unable to provide appropriate management safely at home.
• Liaise with a microbiologist or consultant in communicable disease control if:
  • There is uncertainty about the need for admission in a person with a confirmed microbiological cause on stool culture and sensitivity testing.
  • There is uncertainty about the need for management in a person with moderate or severe suspected travellers' diarrhoea.

How should I manage an adult with gastroenteritis in primary care?

If an adult does not need immediate hospital admission, advise on management and follow up in primary care:

• Provide advice on sources of support and information, such as:
  • The NHS leaflets Diarrhoea and vomiting and Food poisoning.
• Advise on how to monitor fluid intake and prevent/treat dehydration.
  • In healthy adults:
    • Encourage regular fluid intake, and supplement with fruit juice and soups if needed.
  • In adults at increased risk of dehydration (such as the elderly, immunocompromised, those with co-morbid conditions or concurrent illness):
    • Advise on the use of oral rehydration salt (ORS) solution as supplemental fluid.
  • In adults with clinical features of dehydration who can safely be managed at home:
    • Advise to use ORS solution frequently and in small amounts, such as 200–400 mL to be given after every loose motion, dose according to fluid loss, to rehydrate the person.
  • After rehydration:
    • Gradually reintroduce usual diet, advising that small, light, non-fatty, non-spicy meals may be better tolerated.
• Advise that drug treatment with antidiarrhoeal (or antimotility) drugs, antiemetics, and probiotics is not routinely recommended for use in adults in primary care.
  • Antidiarrhoeal drugs may be useful for symptom relief in adults with mild-to-moderate diarrhoea, for example, if rapid resolution would enable the person to resume essential activities. Advise that they are available to purchase over-the-counter, but should not be used if a person has:
    • Blood, mucus, and/or pus in the stools or high fever (suggesting possible dysentery).
    • Shigellosis or confirmed, probable, or suspected Shiga toxin-producing Escherichia coli 0157 (STEC) infection, following stool culture and sensitivity testing.
• Do not routinely prescribe antibiotics to adults with gastroenteritis.
  • Arrange treatment of confirmed microbial pathogens, if appropriate, following stool culture and sensitivity testing. See the section on Management of confirmed cause for more information.
• Advise on methods to prevent transmission of infection:
  • Wash hands thoroughly with liquid soap in warm running water, and dry carefully.
  • Always use a flush toilet, if possible.
    • If a commode or bedpan must be used, it should be handled with gloves, the contents disposed of into the toilet, and the container then washed with hot water and detergent and allowed to dry.
    • Wash hands after going to the toilet and changing nappies, and before preparing, serving, or eating food.
    • Toilet seats, flush handles, wash-hand basin taps, surfaces, and toilet door handles should be cleaned at least once daily with hot water and detergent. A disinfectant and disposable cloth (or one dedicated for toilet use) should be used to clean toilets.
  • Do not share towels and flannels used by the infected person.
  • Wash soiled clothing and bed linen separately from other clothes and at a high temperature (for example 60°C or higher for cotton), after removal of excess faecal matter or vomitus into the toilet. Soaking in disinfectant is not necessary. The washing machine should not be more than half full to allow for adequate washing and rinsing.
  • The PHE leaflet Minimising the spread of gastrointestinal infection provides detailed information on personal hygiene, environmental cleaning, and disposal of soiled materials.
• Advise that the person should not attend work or other institutional/social settings until at least 48 hours after the last episode of diarrhoea or vomiting.
  • Note: for some gastrointestinal infections, longer periods of exclusion are needed, and 'microbiological clearance' with negative stool testing may be required before return to specific settings. See the section on Management of confirmed cause for more information.
  • Note: if cryptosporidiosis or giardiasis is suspected or confirmed, the person should not go swimming for 2 weeks after the last episode of diarrhoea.
• Advise the person/carers on the need for follow up and to seek urgent medical advice if there are:
  • Any features requiring hospital admission or assessment. See the section on Hospital admission for more information.
  • Any new features requiring stool culture testing, such as blood, mucus, and/or pus in the stool (suggesting possible dysentery).
  • Symptoms that do not resolve within the expected timeframe, such as diarrhoea that has not resolved by day 7 —  arrange stool culture testing and consider whether an alternative diagnosis is possible.
• Notify the local health protection team immediately by completing a notification form, if any of the following notifiable diseases or organisms is suspected:
  • Food poisoning (such as suspected Bacillus cereus, Campylobacter spp., Clostridium perfringens, Cryptosporidium spp., Entamoeba histolytica, verocytotoxigenic Escherichia coli (including E. coli O157:H7), Salmonella spp., Giardia lamblia, and Yersinia pestis), including suspected clusters or outbreaks.
  • Haemolytic uraemic syndrome.
  • Infectious bloody diarrhoea, such as Shigella spp.
  • Enteric fever (typhoid or paratyphoid fever).
  • Cholera.

How should I manage gastroenteritis due to a confirmed microbiological cause?

If an adult with gastroenteritis has a specific microbiological cause confirmed after stool culture and sensitivity testings, seek advice from the local health protection team regarding the need for antibiotic treatment or stool testing for microbiological clearance if there is any uncertainty.

• Campylobacteriosis
  • Antibiotic treatment is not usually needed for people with mild symptoms, as infection is usually self-limiting.
  • If symptoms are severe (high fever, bloody and/or high-output diarrhoea) or the person is immunocompromised, consider early prescribing with clarithromycin 250 mg to 500 mg twice daily for 5–7 days, within 3 days of onset of illness. See the section on Clarithromycin in Prescribing information for more information.
• Cryptosporidiosis
  • There is no specific treatment licensed in the UK.
  • Seek specialist advice if the person is severely immunocompromised, owing to the risk of serious and life-threatening complications.
  • Advise the person that they should not go swimming for 2 weeks after the last episode of diarrhoea.
• Amoebiasis or amoebic dysentery
  • Drug treatment is usually recommended for all confirmed cases after specialist advice, such as metronidazole followed by the anti-protozoal drug diloxanide.
  • Seek specialist advice regarding the need for microbiological clearance to confirm treatment success, 1 week after completing treatment.
• Escherichia coli (E. coli)
  • There is no effective antibiotic treatment available for Shiga toxin-producing E. coli (STEC) infection.
  • Seek specialist advice on the need for stool testing for microbiological clearance in people at increased risk of transmission of infection. This includes:
    • Those who cannot ensure personal hygiene at home, work or school.
    • Those attending pre-school groups or nurseries.
    • Those who prepare or serve unwrapped food that is not heated further.
    • Healthcare workers with direct contact with highly susceptible patients, or patients for whom an infection like STEC could have serious consequences.
      • If there is confirmed STEC infection — two consecutive negative stool samples are usually needed, taken at least 24 hours apart, once the person is symptom-free for at least 48 hours, before the person can return to work or other institutional/social settings.
  • Seek specialist advice if there is confirmed STEC infection regarding monitoring for the complication of haemolytic uraemic syndrome.
• Giardiasis
  • 2000 mg once daily for 3 days. Alternatively, 400 mg three times a day for 5 days, or 500 mg twice daily for 7–10 days.
  • Advise the person that they should not go swimming for 2 weeks after the last episode of diarrhoea.
• Salmonellosis (non-typhoidal)
  • Antibiotic treatment is not usually needed.
  • Treat invasive or severe infections if there is a risk of developing invasive infection (e.g. immunocompromised patients, those with haemoglobinopathy, or children under 6 months of age) following specialist advice. 
• Shigellosis
  • Antibiotic treatment is not usually needed for people with mild symptoms.
  • If symptoms are severe (high fever, bloody and/or high-output diarrhoea) or the person is immunocompromised, seek specialist advice on the need for antibiotic treatment.
  • Advise on safe sexual practices if transmission amongst men who have sex with men has resulted in an outbreak.
  • Seek specialist advice on the need for exclusion of cases from childcare or work settings, and the need for microbiological clearance stool testing, which varies depending on the Shigella species.

Contraindications and cautions

• Do not prescribe metronidazole in people with:
  • Known metronidazole or nitroimidazole hypersensitivity.
• Prescribe metronidazole with caution in people with:
  • Cockayne syndrome — cases of severe hepatotoxicity/acute hepatic failure, including cases with a fatal outcome with very rapid onset after treatment initiation in patients with Cockayne syndrome have been reported with products containing metronidazole for systemic use.
    • Only prescribe after careful benefit-risk assessment and only if no alternative treatment is available. Liver function tests must be performed just prior to the start of therapy, throughout and at the end of treatment until liver function is within normal ranges, or until the baseline values are reached.
  • Active or chronic severe peripheral and central nervous system disease, as there is a risk of neurological aggravation.
  • Hepatic encephalopathy — prescribe one-third of the daily dosage once daily.

[EMC, 2025; BNF, 2026]

Adverse effects

• Adverse effects of oral metronidazole include:
  • Rare or very rare — agranulocytosis, arthralgia, anaphylaxis, myalgia, ataxia, darkening of urine, dizziness, drowsiness, encephalopathy, erythema multiforme, headache, hepatitis, jaundice, leucopenia (on prolonged or intensive therapy), liver disorders, neutropenia, pancytopenia, thrombocytopenia, pancreatitis, peripheral neuropathy (on prolonged or intensive treatment), pancreatitis, pruritus, psychotic disorders, rashes, subacute cerebellar syndrome, seizures, and visual disturbances.
  • Frequency not known — anorexia, aseptic meningitis, depressed mood, furred tongue, gastrointestinal disturbances, hearing impairment, nausea, optic neuropathy/neuritis, oral mucositis, taste disturbances, tinnitus, urticaria, vomiting. Metronidazole may interfere with certain blood test results, such as some liver enzymes, triglycerides, and glucose, leading to abnormally low results. One manufacturer of metronidazole advises that QT prolongation has been reported, particularly when co-administered with other drugs which prolong the QT interval.
  • Severe bullous skin reactions such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) or acute generalised exanthematous pustulosis (AGEP) have been reported. If symptoms/signs are present, treatment must be immediately discontinued.
  • The manufacturer advises that patients should be warned that metronidazole may darken urine.

[EMC, 2025; BNF, 2026]

Drug interactions

• Drug interactions associated with oral metronidazole include:
  • Alcohol — some people taking oral metronidazole experience a disulfiram-like reaction (flushing, increased respiratory rate, increased pulse rate, nausea, headache, and dizziness) with alcohol.
    • Although there is no conclusive evidence to support this interaction, warn the person that they might experience this reaction if they drink alcohol whilst taking metronidazole. Alcohol should be avoided during treatment with metronidazole and for at least 48 hours afterwards.
  • Anticoagulants — the anticoagulant effects of warfarin and acenocoumarol can be markedly increased by metronidazole. There is no interaction with heparin. 
    • Monitor the international normalized ratio (INR) if concurrent treatment is indicated, and adjust the anticoagulant dose accordingly.
    • Warn the person of the possible risk of increased bruising and bleeding, and advise them on when to seek medical help.
  • Busulfan — plasma levels of busulfan may be increased leading to toxicity. Avoid high doses of busulfan. If conventional doses of busulfan are given, monitor blood count weekly.
  • Ciclosporin — people receiving concurrent metronidazole and ciclosporin are at risk of elevated serum ciclosporin levels.
    • When co-administration of metronidazole and ciclosporin is necessary, monitor serum ciclosporin and creatinine levels closely.
  • Disulfiram — increases the risk of acute psychosis when given with metronidazole. Also, both drugs can increase the risk of peripheral neuropathy.
  • Ergometrine — metronidazole is predicted to increase the exposure to ergot derivatives, which might lead to ergotism. If concurrent use is unavoidable, be alert for symptoms of ergotism (such as coldness, numbness, or tingling of the hands and feet), and strongly advise patients not to take any further doses and to seek medical advice.
  • Fluorouracil — the toxicity of fluorouracil, but not its efficacy, is increased by metronidazole. Monitor the person for increased toxicity. 
  • Lithium — raised lithium levels accompanied by evidence of possible renal damage have been reported in people treated simultaneously with lithium and metronidazole.
    • Before starting metronidazole in a person taking lithium, seek specialist advice about tapering or stopping lithium treatment.
    • If concurrent treatment is unavoidable, closely monitor plasma concentrations of lithium, creatinine, and electrolytes.
  • Live cholera vaccines — the efficacy of the live vaccine may be affected. Avoid concurrent use and for 14 days before, and for 10 days after, live cholera vaccines.
  • Live typhoid vaccines — the immune response to the vaccine may be reduced. Antibacterials should be stopped from 3 days before to 3 days after receiving live typhoid vaccines.
  • Oral hormonal contraceptives — additional contraceptive precautions are not required during or after courses of metronidazole [CoSRH, 2022].
    • However, advise women on the importance of correct contraceptive practice if they experience vomiting or diarrhoea. For further information, see the section on vomiting or diarrhoea in the CKS topics on Contraception - combined hormonal methods  and Contraception - progestogen-only methods.
  • Phenobarbital or phenytoin — people receiving phenobarbital or phenytoin metabolize metronidazole at a much greater rate than normal, thereby reducing the half-life to approximately 3 hours. In addition, both metronidazole and phenytoin can increase the risk of peripheral neuropathy.
  • One manufacturer's SPC also notes that QT prolongation has been reported (unknown frequency), particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval.
  • Warfarin — the anticoagulant effects of warfarin may be increased by metronidazole.  Monitor the international normalized ratio (INR) and adjust the warfarin dose accordingly. 
• For a complete list of possible drug interactions of metronidazole, see the electronic Medicines Compendium (emc) and the British National Formulary (BNF).

[EMC, 2025; BNF, 2026; Preston, 2026]

Pregnancy and breastfeeding

Pregnancy

• There is inadequate evidence of the safety of metronidazole in pregnancy, but it has been in wide use for many years without apparent ill consequence.
• The manufacturer advises that it should only be used if the benefit outweighs the risks and advises against short, high-dose regimens.

Breastfeeding

• Significant amounts of metronidazole are excreted in breast milk. The manufacturer advises against the use of short, high-dose regimens.

[EMC, 2025; BNF, 2026]

Contraindications and cautions

• Do not prescribe clarithromycin to people with:
  
  • A history of QT prolongation or ventricular cardiac arrhythmia, including Torsades de pointes.
  • Conditions that predispose to QT interval prolongation, such as electrolyte disturbances (hypokalaemia or hypomagnesaemia) or the use of some medications that prolong the QT interval.
  • Severe hepatic impairment in combination with renal impairment.
• Prescribe clarithromycin with caution to people with:
  • Hepatic impairment (or concurrently receiving potentially hepatotoxic drugs).
  • Moderate to severe renal impairment.
    • For immediate-release preparations: if creatinine clearance (CrCl) is less than 30 mL/minute, prescribe half the normal dose and use for a maximum duration of 14 days.
    • For modified-release preparations: if CrCl is 30–60 mL/minute, prescribe half the normal dose. Avoid if CrCl is less than 30 mL/minute.
  • Myasthenia gravis — macrolides may aggravate weakness symptoms.
  • Other risk factors for QT prolongation, such as:
    • Coronary artery disease, severe cardiac insufficiency, conduction disturbances, or clinically relevant bradycardia.
    • The use of some medications associated with QT prolongation. 

[BNF, 2026; EMC, 2026]

Adverse effects

• Cardiac — cardiac arrest, atrial fibrillation, QT interval prolongation (uncommon).
  • Rarely: Torsades de pointes, ventricular tachycardia, ventricular fibrillation.
• Gastrointestinal — diarrhoea, vomiting, dyspepsia, nausea, abdominal pain (common).
  • Rarely: pancreatitis, pseudomembranous colitis. For more information, see the CKS topic on Diarrhoea - antibiotic associated.
• Nervous system — headache, dysgeusia (common), dizziness, somnolence, tremor (uncommon).
  • Rarely: convulsions, paraesthesia.
• Psychiatric — insomnia (common), anxiety, nervousness (uncommon).
  • Rarely or very rarely: psychotic disorders, depression, mania, hallucination.
• Skin — rash, hyperhidrosis (common), pruritus, urticaria (uncommon).
  • Rarely, or very rarely: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalised exanthematous pustulosis (AGEP).
• Other adverse effects reported rarely, or very rarely, include: 
  • Anaphylaxis.
  • Deafness.
  • Hepatic failure, jaundice.
  • Pancreatitis. 
  • Renal failure, interstitial nephritis.
  • Rhabdomyolysis, myopathy.

[BNF, 2026; EMC, 2026]

Drug interactions

Possible drug interactions with clarithromycin include:

• Drugs that cause hypokalaemia — these can increase the risk of torsade de pointes when given with clarithromycin. For example:
  • Aminophylline — monitor potassium concentrations closely.
  • Diuretics (such as furosemide, bendroflumethiazide) — monitor potassium concentrations closely.
  • Beta-2 agonists (salbutamol, salmeterol) — monitor potassium concentrations closely.
  • Corticosteroids (such as prednisolone, beclometasone) — clarithromycin is also predicted to increase corticosteroid concentrations. Monitor potassium concentrations closely and for corticosteroid adverse effects
• Drugs that prolong the QT interval (such as amiodarone, haloperidol, domperidone, methadone) — all macrolides can prolong the QT interval, and caution is advised with concurrent use. If concurrent use is unavoidable consider ECG monitoring.   
  • Concurrent use is contraindicated with domperidone, ivabradine, mizolastine, astemizole, cisapride, and pimozide.
• Clarithromycin is predicted to increase the exposure of drugs metabolized by CYP3A4, for example:
  • Carbamazepine — monitor carbamazepine concentrations and adjust the dose accordingly
  • Ciclosporin — monitor the concentration and effects of ciclosporin more frequently if clarithromycin is started or stopped, adjusting the ciclosporin dose as necessary.
  • Digoxin — monitor for adverse effects, measure digoxin concentrations, and adjust dose if necessary. 
  • Diltiazem, verapamil — monitor for adverse effects and reduce dose if necessary. 
  • Eplerenone — concurrent use is contraindicated.
  • Fesoterodine, solifenacin — reduce dose. Concurrent use is contraindicated in people with renal impairment or hepatic impairment.  
  • Ivabradine — concomitant treatment is contra-indicated.
  • Lercanidipine — concurrent use is contraindicated. 
  • Oral anticoagulants — monitor for adverse effects. Dose reductions may be necessary.
  • Quetiapine — concurrent use is contraindicated. If necessary, monitor for adverse effects. 
  • Sildenafil, tadalafil — dose reductions may be necessary. 
  • Statins —  concurrent administration with clarithromycin increases their plasma levels and the risk of myopathy.
    • Lovastatin, simvastatin —  concurrent use is contraindicated. If treatment with clarithromycin cannot be avoided, stop treatment with statin temporarily.
    • Atorvastatin — avoid concurrent use with clarithromycin. If concurrent use cannot be avoided, prescribe the lowest dose of atorvastatin.
  • Ticagrelor — avoid concurrent use. 
• CYP3A enzyme inducers (rifampicin, carbamazepine, phenobarbital) — these may induce the metabolism of clarithromycin, resulting in sub-therapeutic levels.
  • It may be necessary to monitor the levels of these drugs, as CYP3A is inhibited by clarithromycin leading to higher plasma levels of the inducer.
• Edoxaban — manufacturer advises caution with concurrent treatment with edoxaban, particularly in those with a high risk of bleeding.

[EMC, 2026; Preston, 2026]

Pregnancy and breastfeeding

Pregnancy

• The safety of clarithromycin in pregnancy has not been established. Avoid (especially in the first trimester), unless the potential benefits outweigh the possible risks.

Breastfeeding

• Clarithromycin is excreted into breastmilk in small amounts. An exclusively breastfed infant would receive about 1.7% of the maternal weight-adjusted dose of clarithromycin.
• Because of the low levels of clarithromycin in breastmilk and safe administration directly to infants, it is acceptable in breastfeeding mothers. The small amounts in milk are unlikely to cause adverse effects in the infant. Monitor the infant for possible effects on the gastrointestinal flora, such as diarrhoea, and candidiasis [LactMed, 2022]

[BNF, 2026; EMC, 2026]