Diarrhoea usually occurs when fluid can't be absorbed from the contents ofyour bowel, or when extra fluid is secreted into your bowel, causing watery poo.

Short-term diarrhoea

Diarrhoea is usually a symptom of a bowel infection (gastroenteritis) , whichcanbe caused by:

  • a virus such as norovirus orrotavirus
  • 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 ofshort-term diarrhoea include:

  • feelings ofanxiety
  • drinking too much alcohol
  • a food allergy
  • appendicitis
  • damage to the lining of the intestines as a result of radiotherapy


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

  • antibiotics
  • antacid medicines that contain magnesium
  • some chemotherapy medicines
  • non-steroidal anti-inflammatory drugs (NSAIDs)
  • selective serotonin reuptake inhibitors (SSRIs)
  • statins cholesterol-lowering medicines
  • laxatives medicine used tohelp empty your bowels

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

Long-term diarrhoea

Conditions that can cause persistent diarrhoea include:

  • irritable bowel syndrome (IBS) a poorly understood condition that affects the normal functions of the bowel
  • inflammatory bowel disease conditions that cause the gut to become inflamed, such as Crohn's disease and ulcerative colitis
  • coeliac disease a digestive condition where you have an adverse reaction to gluten
  • bile acid malabsorption where bile produced by the liver builds up in the digestive system
  • chronic pancreatitis inflammation of the pancreas
  • diverticular disease where small bulges or pockets develop in the lining of the intestine
  • bowel cancer this can cause diarrhoea and blood in your stools

Persistent diarrhoea can also sometimes occurafter surgery on the stomach, such as a gastrectomy .

Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2016