Symptoms of diarrhoea

Diarrhoea is when you need to poo more often than you usually do in one day. And your poo is more loose and watery than usual.

It can be a mild side effect of treatment for cancer, but for some people it can be severe. Tell your doctor, nurse, or contact your hospital advice line if you have diarrhoea. 

Changes to look out for include:

  • an increase in the number of times you have a poo (bowel movements) each day

  • an increase in the amount (volume) of poo you have in a day

  • a change in the way your poo looks - if it goes from solid to soft or watery

Other symptoms you might notice are:

  • needing to get to the toilet urgently

  • a bloated feeling in the tummy (abdomen)

  • cramping pains in your tummy

  • feeling or being sick

  • loss of appetite

  • feeling weak and tired

  • losing weight

If you have a colostomy Open a glossary item or ileostomy Open a glossary item and you are emptying your stoma bag Open a glossary item more often than normal, it might be a sign that you have diarrhoea.

Symptoms of severe diarrhoea

Severe diarrhoea can cause you to lose a lot of fluid and become dehydrated. This can make you very ill if you don't have treatment. 

It is important to see your doctor if you have any of the following symptoms:

  • a high temperature (fever) or chills

  • signs of dehydration such as feeling very thirsty, a rapid heartbeat, feeling or being sick, headaches, and dark urine

  • blood or mucus in your poo

  • severe cramping and tummy pain

When to contact your doctor or nurse

Contact your healthcare team if you have 2 or more loose bowel movements than usual over 24 hours. Let them know if you think you are losing more fluid than you are able to drink.

Sometimes it can be hard to know when to call your doctor or nurse because you don’t want to bother them. You might feel embarrassed about talking about your diarrhoea. But they are used to this and will want to help you. They can advise you on how to manage your diarrhoea and might recommend some medicines.

  • Diarrhoea in adult cancer patients: ESMO Clinical Practice Guidelines
    P Bossi and others
    Annals of Oncology October 2018. Volume 29, Supplement 4, Pages iv126 to iv142

  • Guidelines for the investigation of chronic diarrhoea in adults: British Society of Gastroenterology (3rd Edition)
    R P Arasaradnam and others
    Gut, 2018. Volume 67, Issue 8, Pages 1380 to 1399

  • BMJ Best Practice Assessment of chronic diarrhoea
    S Campbell and R Kalla
    BMJ Publishing Group Ltd, last updated April 2023

  • BMJ Best Practice Assessment of acute diarrhoea
    T N Lunsford
    BMJ Publishing Group Ltd, last updated August 2025

  • Diarrhoea – adult’s assessment
    National Institute for Health and Care Excellence (NICE), last updated November 2023

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk if you would like to see the full list of references we used for this information.

Last reviewed: 
09 Sep 2025
Next review due: 
09 Sep 2028

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