Causes of diarrhoea 

Diarrhoea usually occurs when fluid cannot be absorbed from the contents of your bowel, or when extra fluid is secreted into your bowel, causing watery poo.

Short-term diarrhoea

Diarrhoea is usually a symptom of gastroenteritis (a bowel infection), which can be caused by:

  • a virus – such as norovirus or rotavirus
  • bacteria – such as campylobacter, Clostridium difficile (C. difficile), Escherichia coli (E. coli), salmonella or shigella; these can all cause food poisoning
  • parasites – such as the Giardia intestinalis parasite that causes giardiasis

Other possible causes of short-term diarrhoea include:

Medicines

Diarrhoea can also sometimes be a side effect of a medication, including:

The patient information leaflet that comes with your medicine should state whether diarrhoea is a possible side effect.

You can also use the medicines A-Z to find out about your medicine.

Long-term diarrhoea 

Conditions that can cause persistent diarrhoea include:

Persistent diarrhoea can also sometimes occur following surgery on the stomach, such as a gastrectomy. This is an operation to remove part of the stomach – for example, as a treatment for stomach cancer.

Page last reviewed: 26/11/2014

Next review due: 26/11/2016