Diagnosing ulcerative colitis 

To diagnose ulcerative colitis, your GP will first ask about your symptoms, general health and medical history.

They will also physically examine you, checking for signs such as paleness (caused by anaemia) and tenderness in your tummy (caused by inflammation).

A stool sample can be checked for signs of infection, as gastroenteritis (infection of the stomach and bowel) can sometimes have similar symptoms to ulcerative colitis. Blood tests may also be carried out to check for anaemia and to see if there is inflammation on any part of your body.

Further tests

If your GP suspects you may have inflammatory bowel disease (a term mainly used to describe two diseases: ulcerative colitis or Crohn's disease), you may be referred to hospital for further tests. These could include an X-ray and a detailed examination of your rectum and colon.

The two types of examination you may have are described below.


A diagnosis of ulcerative colitis can be confirmed by examining the level and extent of bowel inflammation. This is initially done by using a sigmoidoscope, which is a flexible tube containing a camera that is inserted into your rectum (bottom).

A sigmoidoscopy can also be used to remove a small sample of tissue from your bowel, so it can be tested in a laboratory. This is known as a biopsy.

The procedure is not painful, but it can be uncomfortable, and you can be given a sedative to help you relax. It usually takes around 15 minutes and you can often go home the same day.

A sigmoidoscope is only capable of looking at the rectum and lower part of the colon. If it is thought your ulcerative colitis has affected more of your colon, another examination will be required. This is known as a colonoscopy.


A colonoscopy uses a longer and more flexible tube called the colonoscope, which allows your entire colon to be examined. As with a sigmoidoscope, a colonoscope can also be used to obtain a biopsy sample.

Before having a colonoscopy, your colon needs to be completely empty. Therefore, you will need to take strong laxatives beforehand.

A colonoscopy is not painful, but you may feel some initial discomfort. You will be given sedatives to help you relax. The procedure takes around half an hour, after which you will be able to go home.

What happens during a colonoscopy?

A colorectal surgeon explains what happens during a colonoscopy, a procedure which examines the large bowel, the colon or the rectum.

Media last reviewed: 26/05/2015

Next review due: 26/05/2017

Page last reviewed: 20/03/2014

Next review due: 20/03/2016