What is ulcerative colitis?

What is ulcerative colitis?

Ulcerative colitis (UC) is a chronic (long-term) inflammatory condition primarily affecting the large intestine (the bowel and rectum).1,2

In ulcerative colitis, the inner lining of the large intestine (also called the colon) and rectum can become inflamed, causing ulcers, which may bleed and produce mucus.3 The colon then can’t absorb liquid effectively, leading to diarrhoea. It also can’t hold as much waste as normal, so bowel movements can be more frequent (six or more times a day).3

Symptoms of ulcerative colitis

The symptoms of ulcerative colitis depend on how much of the colon is inflamed and how severe the inflammation is, and they can change over time. Having weeks or months with few or no symptoms is known as ‘remission’ and times with active symptoms are relapses or ‘flare-ups’. The impact on everyday life can be significant.2

The most common symptoms are:2,3

Diarrhoea or needing the toilet urgently

Your poo may be looser than normal, more frequent than is usual for you, and blood or mucus may be present

Stomach pains

Cramping pains in the lower abdomen

Fatigue, tiredness or feeling generally unwell

Extreme tiredness, raised temperature, feeling feverish


Bleeding from the anus, blood in your poo


Difficulty passing poo or completely empty the bowel

Loss of appetite, weight loss, anaemia

You may eat less when you feel unwell, and anaemia is likely if you are losing blood in your poo

Types of ulcerative colitis

UC is divided into three main types according to how much of the large intestine is affected. The type of UC can affect which symptoms you have, and which treatment you are offered.3

Infographic showing the rectum, highlighted from the rest of the large intestine.

Affects the rectum, the last part of the bowel

Infographic showing the rectum and left side of the colon, highlighted from the rest of the large intestine.
Left-sided (distal) colitis

Affects the rectum and the left side of the colon (the distal or ‘descending’ part of the colon)

Infographic showing the colon highlighted.
Pancolitis (total colitis)

The whole colon is affected

In severe ulcerative colitis, patients can develop a narrowing in the bowel (a stricture) which may require surgery.

In some rare cases, serious complications can occur, such as toxic megacolon (the gut wall gets thin and fills with gas) which carries risk of a perforation or rupture in the bowel.3

Outside the gut

Complications of UC that affect areas outside the digestive tract are sometimes called ‘extraintestinal’ symptoms, such as:3

  • Bones can become thinner and weaker
  • Skin may become inflamed
  • Eyes may become inflamed

Always mention any new or changing symptoms you have to your doctor – even if they are not related to UC they should be addressed if they affect your quality of life.

A patient consulting with an IBD nurse and discussing her medical records

Management, treatment and monitoring

If you have been diagnosed with ulcerative colitis or Crohn’s disease you might want to find out about

A woman suffering from stomach pain, a symptom of IBD
An elderly patient consulting an IBD specialist doctor and discussing his condition and possible treatment options
A patient interacting with her IBD healthcare team in the NHS
A man with IBD sleeping on the tube

Patient advocacy groups

You can find out more about inflammatory bowel disease from these independent organisations

Crohn’s and Colitis UK

The Crohn’s & Colitis UK website provides information on a range of issues relating to both Crohn’s disease and ulcerative colitis, with helpful guides about the conditions, how they are treated and how to live with them. The charity provides a range of other support, including helpline services, local volunteer networks and an active membership community of over 40,000 people

IBDrelief logo.

IBDrelief provides information about various aspects of all types of IBD. It provides help with understanding the disease, its treatments and living with IBD, and shares first-hand accounts from people with IBD

*IBDrelief patient survey data from 167 respondents with IBD in the UK. 58% of respondents who did not discuss emotional wellbeing with their consultant gave a lack of time as the reason.4


CD = Crohn’s disease; IBD = inflammatory bowel disease; UC = ulcerative colitis.

  1. NHS. Inflammatory bowel disease. www.nhs.uk/conditions/inflammatory-bowel-disease/. Accessed October 2023.
  2. IBDrelief. Impact of IBD on physical and emotional health: Findings from an IBDrelief survey. Available at www.ibdrelief.com/impact-of-ibd-on-physical-and-emotional-health. Accessed October 2023.