Diarrhoea - Diagnosing diarrhoea

Most cases of diarrhoea get better within a week and you may not need to visit your GP.

Read more about when to visit your GP if you have diarrhoea.

The information below explains what will happen if you need to see your GP.

Identifying the cause

To identify what is causing your diarrhoea, your GP may ask questions, such as:

• what your stools are like – for example, if they are very watery or contain blood
• how often you need to go to the toilet
• whether you have other symptoms, such as a high temperature (fever) 
• whether you have been in contact with anyone else who has diarrhoea or have recently travelled abroad, as this may mean you have picked up an infection
• whether you have recently eaten out anywhere, as this may mean you have food poisoning
• whether you are taking medication and if it has recently changed 
• whether you have been stressed or anxious recently

Stool sample

Your GP may ask you for a stool sample, so it can be analysed for signs of an infection, if you have:

• persistent diarrhoea that has lasted more than two weeks
• blood or pus in your stools 
• symptoms that affect your whole body, such as a fever or dehydration
• a weakened immune system – for example, because you have HIV 
• recently travelled abroad
• recently been in hospital or been taking antibiotics

Find out how to collect and store a stool sample.

Blood tests

Your GP may suggest that you have some blood tests if they suspect that an underlying health condition is causing your diarrhoea.

For example, your blood can be tested for signs of inflammation, which may suggest inflammatory bowel disease.

Read more about the possible causes of diarrhoea.

Rectal examination

Your GP may recommend a digital rectal examination (DRE) if you have unexplained persistent diarrhoea, particularly if you are over 50.

During a DRE, your GP will insert a gloved finger into your bottom to feel for any abnormalities. It can be useful for diagnosing conditions that affect your rectum and bowel.

Further investigations

If you have persistent diarrhoea and your GP is unable to find the cause, they may refer you to your local hospital for further investigation.

You may have:

• a sigmoidoscopy – an instrument called a sigmoidoscope (a thin, flexible tube with a small camera and light on one end) is inserted into your bottom and up into your bowel
• a colonoscopy – a similar procedure that uses a larger tube called a colonoscope to examine your entire bowel