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 have had diarrhoea
• whether you have other symptoms, such as a fever 
• whether you have been in contact with anyone else who has diarrhoea (you may have caught an infection) 
• whether you have recently eaten out anywhere (you may have food poisoning)
• whether you have recently travelled abroad (to rule out travellers’ diarrhoea)
• whether you are taking medication and if it has recently changed 
• whether you have been stressed or anxious recently 
• how much coffee and alcohol you drink 

Stool sample

Your GP may ask you for a stool sample so it can be analysed for bacteria or parasites if you have:

• persistent diarrhoea that has lasted more than a week
• other symptoms, such as blood or pus in your stools 
• symptoms that affect your whole body, such as 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

If you have unexplained persistent diarrhoea or if you are over the age of 50, your GP may recommend a digital rectal examination (DRE).

During a DRE, your GP will insert a gloved finger into your anus (back passage) and rectum to feel for any abnormalities. It can be useful in diagnosing conditions that affect your rectum and bowels.

Further investigations

If your GP is unable to find the cause of your diarrhoea, they may refer you to your local hospital for further investigations.

For example, 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 rectum and up into your bowel
• a colonoscopy – a similar procedure that uses a larger tube called a colonoscope to examine your entire bowel