Assessing diarrhoea

If you have diarrhoea your doctor or nurse will ask you questions and might do tests to assess how severe your diarrhoea is and whether it needs treatment.

Effects of diarrhoea on the body

Diarrhoea can affect your body in different ways:


Diarrhoea can cause dehydration. When you have diarrhoea, food passes quickly through the bowel before your body absorbs the vitamins, minerals and water. And fluid is also drawn out of the cells in your body into the bowel. The fluid is released in your poo (stool or faeces). 

Losing large amounts of fluid can be dangerous for your body. And you can feel very weak and tired.


Along with fluid, you also lose important chemicals from the cells of your body. These chemicals are called electrolytes. They include sodium, potassium, and calcium.

The electrolytes must be in a certain balance for the body to work normally. When the electrolytes get out of balance it can be harmful to your kidneys and other organs in your body.

Sore skin

The salts in the diarrhoea can also make the skin around your anus very sore after a while.

Grading the diarrhoea

Health professionals use a grading system for diarrhoea from 1 to 4. Grade 1 is mild diarrhoea and grade 4 is the most severe. This can help your doctor or nurse to plan the best treatment for you.

Diarrhoea can be difficult to control. This depends on what the cause is.

Your doctor or nurse might:

  • assess how severe your diarrhoea is
  • find out what is causing it
  • examine you and possibly arrange some other tests and investigations
  • prescribe you some medicines to help
  • give you advice about ways to help yourself

Talking about your diarrhoea

You might find it hard to talk about having diarrhoea. You may feel embarrassed or upset, or worried about what the diarrhoea means. These feelings are very natural.

Remember that your doctors and nurses will be aware of your likely worries and are used to talking about them. They can reassure you and suggest ways of managing your diarrhoea.

Some people say that diarrhoea is one of the hardest aspects of cancer treatment to cope with. So it is very important that you get some help.

If you find it difficult to talk to your doctors or nurses, it might help to write down the problems you have. You can give the list to your doctor or nurse to read. It can also help to have a friend or relative go with you and do the talking.

If you have treatment in an open day unit, you can ask to go into a private room to discuss your diarrhoea. Your doctors and nurses are aware that you might want to talk in private sometimes, so don’t be afraid to ask.

Questions your doctor or nurse might ask

  • How long have you had diarrhoea?
  • How many times a day and night are you opening your bowels?
  • Are you taking any medicines?
  • What does your poo look like?
  • Does it happen at particular times such as after you have eaten or after your cancer treatment
  • Are you taking any medicines to help?
  • How much is your diarrhoea stopping you from doing day to day things?

Your family and friends might be able to help if you feel too tired and don’t feel up to answering questions.

Although you might find it embarrassing or inconvenient to speak to your doctor or nurse about your diarrhoea, the sooner they can treat it the more comfortable you will feel.

Last reviewed: 
25 Jul 2019
  • Assessment and management of diarrhoea in adults
    National Institute for Health and Care Excellence (NICE), December 2018

  • Symptom management in advanced cancer (4th edition)
    R Twycross, A Wilcock and S Toller
    Radcliffe Medical Press Ltd, 2009

  • Cancer: Principles and practice of oncology (11th edition)
    VT De Vita, S Hellman and SA Rosenberg
    Wolters Kluwer, 2019

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