About ulcerative colitis

Ulcerative colitis is a long-term condition, where the colon and rectum become inflamed.

The colon is the large intestine (bowel), and the rectum is the end of the bowel where stools are stored.

Small ulcers can develop on the colon's lining, and can bleed and produce pus.

Symptoms of ulcerative colitis

The main symptoms of ulcerative colitis are:

  • recurring diarrhoea, which may contain blood, mucus or pus
  • abdominal pain
  • needing to empty your bowels frequently

You may also experience fatigue (extreme tiredness), loss of appetite and weight loss.

The severity of the symptoms varies, depending on how much of the rectum and colon is inflamed and how severe the inflammation is. For some people, the condition has a significant impact on their everyday lives.

Symptoms of a flare-up

Some people may go for weeks or months with very mild symptoms, or none at all (known as remission), followed by periods where the symptoms are particularly troublesome (known as flare-ups or relapses).

During a flare-up, some people with ulcerative colitis also experience symptoms elsewhere in their body. For example, some people develop:

  • painful and swollen joints (arthritis)
  • mouth ulcers
  • areas of painful, red and swollen skin
  • irritated and red eyes

In severe cases, defined as having to empty your bowels 6 or more times a day, additional symptoms may include:

  • shortness of breath
  • a fast or irregular heartbeat
  • a high temperature (fever)
  • blood in your stools becoming more obvious

In most people, no specific trigger for flare-ups is identified, although a gut infection can occasionally be the cause. Stress is also thought to be a potential factor.

Read more about living with ulcerative colitis.

When to seek medical advice

You should see your GP as soon as possible if you have symptoms of ulcerative colitis and you haven't been diagnosed with the condition.

They can arrange blood or stool sample tests to help determine what may be causing your symptoms. If necessary, they can refer you to hospital for further tests.

Read more about diagnosing ulcerative colitis.

If you've been diagnosed with ulcerative colitis and think you may be having a severe flare-up, contact your GP or care team for advice. You may need to be admitted to hospital.

If you can't contact your GP or care team, call NHS 24 111 service or contact your local out-of-hours service.

What causes ulcerative colitis?

Ulcerative colitis is thought to be an autoimmune condition. This means the immune system – the body's defence against infection – goes wrong and attacks healthy tissue.

The most popular theory is that the immune system mistakes harmless bacteria inside the colon for a threat and attacks the tissues of the colon, causing it to become inflamed.

Exactly what causes the immune system to behave in this way is unclear. Most experts think it's a combination of genetic and environmental factors.

Read more about the causes of ulcerative colitis.

Who's affected?

It's estimated that around 1 in every 420 people living in the UK has ulcerative colitis; this amounts to around 146,000 people.

The condition can develop at any age, but is most often diagnosed in people from 15 to 25 years old.

It's more common in white people of European descent (especially those descended from Ashkenazi Jewish communities) and black people. The condition is rarer in people from Asian backgrounds (although the reasons for this are unclear).

Both men and women seem to be equally affected by ulcerative colitis.

How ulcerative colitis is treated

Treatment for ulcerative colitis aims to relieve symptoms during a flare-up and prevent symptoms from returning (known as maintaining remission).

In most people, this is achieved by taking medication such as:

  • aminosalicylates (ASAs)
  • corticosteroids
  • immunosuppressants

Mild to moderate flare-ups can usually be treated at home. However, more severe flare-ups need to be treated in hospital to reduce the risk of serious complications, such as the colon becoming stretched and enlarged or developing large ulcers. Both of these can increase the risk of developing a hole in the bowel.

If medications aren't effective at controlling your symptoms, or your quality of life is significantly affected by your condition, surgery to remove your colon may be an option.

During surgery, your small intestine will either be diverted out of an opening in your abdomen (known as an ileostomy), or used to create an internal pouch that's connected to your anus (known as an ileo-anal pouch).

Read more about:

Causes of ulcerative colitis

The exact cause of ulcerative colitis is unknown, although it's thought to be the result of a problem with the immune system.

Autoimmune condition

The immune system is the body's defence against infection. Many experts believe ulcerative colitis is an autoimmune condition (when the immune system mistakenly attacks healthy tissue).

The immune system normally fights off infections by releasing white blood cells into the blood to destroy the cause of the infection. This results in inflammation (swelling and redness) of body tissue in the infected area.

In ulcerative colitis, a leading theory is that the immune system mistakes "friendly bacteria" in the colon – which aid digestion – as a harmful infection, leading to the colon and rectum becoming inflamed.

Alternatively, some researchers believe a viral or bacterial infection triggers the immune system, but for some reason it doesn't "turn off" once the infection has passed and continues to cause inflammation.

It's also been suggested that no infection is involved and the immune system may just malfunction by itself, or that there's an imbalance between good and bad bacteria within the bowel.


It also seems inherited genes are a factor in the development of ulcerative colitis. Studies have found that more than 1 in 4 people with ulcerative colitis has a family history of the condition.

Levels of ulcerative colitis are also a lot higher in certain ethnic groups, further suggesting that genetics are a factor.

Researchers have identified several genes that seem to make people more likely to develop ulcerative colitis, and it's believed that many of these genes play a role in the immune system.

Environmental factors

Where and how you live also seems to affect your chances of developing ulcerative colitis, which suggests environmental factors are important.

For example, the condition is more common in urban areas of northern parts of Western Europe and America.

Various environmental factors that may be linked to ulcerative colitis have been studied, including air pollution, medication and certain diets.

Although no factors have so far been identified, countries with improved sanitation seem to have a higher population of people with the condition. This suggests that reduced exposure to bacteria may be an important factor.

Diagnosing ulcerative colitis

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

They'll 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's 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 2 diseases: ulcerative colitis or Crohn's disease), you may be referred to hospital for further tests.

These could include an X-ray or computerised tomography (CT) scan to rule out serious complications and a detailed examination of your rectum and colon.

The 2 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, a thin, flexible tube containing a camera that's 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 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.

During this procedure, only the rectum and lower part of the colon are examined. If it's 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 flexible tube containing a camera called a colonoscope, which allows your entire colon to be examined. A biopsy sample can also be taken.

Before having a colonoscopy, your colon needs to be completely empty so you'll need to take strong laxatives beforehand.

A colonoscopy can be uncomfortable, but you'll be given sedatives and pain medications to help you relax and make the procedure as painless as possible. The procedure takes around half an hour and you'll be able to go home the same day.

Treating ulcerative colitis

Treatment for ulcerative colitis depends on how severe the condition is and how often your symptoms flare up.

The main aims of treatment are to:

  • reduce symptoms, known as inducing remission (a period without symptoms)
  • maintain remission

This usually involves taking various types of medication, although surgery may sometimes be an option.

Your treatment will normally be provided by a range of healthcare professionals, including:

  • specialist doctors – such as gastroenterologists or surgeons
  • GPs
  • specialist nurses

Your care will often be co-ordinated by your specialist nurse and your care team, and they'll usually be your main point of contact if you need help and advice.

The various treatments for ulcerative colitis are outlined below. 


Aminosalicylates (5-ASAs), such as sulphasalazine or mesalazine, are medications that help to reduce inflammation. They're usually the first treatment option for mild or moderate ulcerative colitis.

5-ASAs can be used as a short-term treatment for flare-ups. They can also be taken long term, usually for the rest of your life, to maintain remission.

5-ASAs can be taken:

  • orally – by swallowing a tablet or capsule
  • as a suppository – a capsule that you insert into your rectum (bottom), where it dissolves
  • through an enema – where fluid is pumped into your large intestine

How you take 5-ASAs depends on the severity and extent of your condition.

These medications rarely have side effects, but some people may experience:


Corticosteroids, such as prednisolone, are a more powerful type of medication used to reduce inflammation. They can be used with or instead of 5-ASAs to treat a flare-up if 5-ASAs alone aren't effective.

Like 5-ASAs, steroids can be administered orally, or through a suppository or enema.

However, unlike 5-ASAs, corticosteroids aren't used as a long-term treatment to maintain remission because they can cause potentially serious side effects, such as osteoporosis (weakening of the bones) and cataracts (cloudy patches in the lens of the eye) when used for a long time.

Side effects of short-term steroid use can include:

  • acne
  • weight gain
  • increased appetite
  • mood changes (such as becoming more irritable)
  • insomnia (difficulty sleeping)

Read more about the side effects of corticosteroids.


Immunosuppressants, such as tacrolimus and azathioprine, are medications that reduce the activity of the immune system. They're usually given as tablets to treat mild or moderate flare-ups, or maintain remission if your symptoms haven't responded to other medications.

Immunosuppressants can be very effective in treating ulcerative colitis, but they often take a while to start working (usually between two and three months).

The medicines can make you more vulnerable to infection, so it's important to report any signs of infection, such as fever or sickness, promptly to your GP.

They can also lower the production of red blood cells, making you prone to anaemia. You'll need regular blood tests to monitor your blood cell levels and to check for any other problems.

Treating severe flare-ups

While mild or moderate flare-ups can usually be treated at home, more severe flare-ups should be managed in hospital to minimise the risk of dehydration and potentially fatal complications, such as your colon rupturing.

In hospital, you'll be given medication and sometimes fluids intravenously (directly into a vein). The medication you have will usually be a type of corticosteroid or an immunosuppressant medication called infliximab or ciclosporin.


Ciclosporin works in the same way as other immunosuppressant medications (see above) – by reducing the activity of the immune system. However, it's more powerful than the medications used to treat milder cases of ulcerative colitis and starts to work much sooner (normally within a few days).

Ciclosporin is given slowly through a drip in your arm (known as an infusion) and treatment will usually be continuous, for around seven days.

Side effects of intravenous ciclosporin can include:

  • a tremor (an uncontrollable shaking or trembling of part of the body)
  • excessive hair growth
  • fatigue (extreme tiredness)
  • swollen gums
  • feeling and being sick
  • diarrhoea

Ciclosporin can also cause more serious problems such as high blood pressure and reduced kidney and liver function, but you will be monitored regularly during treatment to check for signs of these.

Biologic medications

Infliximab, adalimumab, golimumab and vedolizumab are medications that reduce inflammation of the intestine by targeting proteins which the immune system uses to stimulate inflammation. These medications block these receptors and reduce inflammation.

They may be used to treat adults with moderate to severe ulcerative colitis, if other options aren't suitable or working. Infliximab may also be used to treat children or young people aged 6-17 with severe ulcerative colitis (see below).

The treatment is given for 12 months unless the medication isn't working well.

Read the full NICE guidelines on:


Infliximab is given as an infusion over the course of one to two hours. You'll be given further infusions after two weeks, and again after six weeks. Infusions are then given every eight weeks, if treatment is still required.

Common side effects of infliximab can include:

  • increased risk of infection – report any symptoms of a possible infection, such as coughs, high temperature or sore throat, to your GP
  • vertigo (the sensation you or the environment around you is moving) and dizziness
  • an allergy-like reaction, causing breathing difficulties, urticaria (hives) and headaches

In most cases, a reaction to the medication occurs in the first two hours after the infusion has finished. However, some people experience delayed reactions days, or even weeks, after an infusion. If you begin to experience the symptoms listed above after having infliximab, seek immediate medical assistance.

You'll be carefully monitored after your first infusion and, if necessary, powerful anti-allergy medication, such as epinephrine, may be used.

Infliximab isn't usually suitable for people with a history of tuberculosis (TB) or hepatitis B and needs to be used with caution in those with HIV or hepatitis C. This is because there have been a number of cases where infliximab has "reactivated" dormant infections. The medication is also not recommended for people with a history of heart disease or multiple sclerosis.


If you have frequent flare-ups that have a significant effect on your quality of life, or you have a particularly severe flare-up that isn't responding to medication, surgery may be an option.

Surgery for ulcerative colitis involves permanently removing the colon (known as a colectomy).

During the operation, your small intestine will be used to pass waste products out of your body instead of your colon. This can be achieved by creating:

  • an ileostomy – where the small intestine is diverted out of a hole made in your abdomen. Special bags are placed over this opening, to collect waste materials after the operation
  • an ileo-anal pouch (also known as a J-pouch) – where part of the small intestine is used to create an internal pouch that is then connected to your anus, allowing you to pass stools normally

Ileo-anal pouches are increasingly used because an external bag to collect waste products isn't required.

As the colon is removed, ulcerative colitis can't recur after surgery. However, it's important to consider the risks of surgery and the impact of having a permanent ileostomy or ileo-anal pouch.

Read more about ileostomies and ileo-anal pouches.

Complications of ulcerative colitis

If you have ulcerative colitis, you could develop further problems.

Some of the main complications of ulcerative colitis are described below.


People with ulcerative colitis are at an increased risk of developing osteoporosis, when the bones become weak and are more likely to fracture.

This isn't directly caused by ulcerative colitis, but can develop as a side effect of the prolonged use of corticosteroid medication. It can also be caused by the dietary changes someone with the condition may take – such as avoiding dairy products, if they believe it could be triggering their symptoms.

If you're thought to be at risk of osteoporosis, the health of your bones will be regularly monitored. You may also be advised to take medication or supplements of vitamin D and calcium to strengthen your bones.

Read more about treating osteoporosis.

Poor growth and development

Ulcerative colitis, and some of the treatments for it, can affect growth and delay puberty.

Children and young people with ulcerative colitis should have their height and body weight measured regularly by healthcare professionals. This should be checked against average measurements for their age.

These checks should be carried out every 3-12 months, depending on the person's age, the treatment they're having and the severity of their symptoms.

If there are problems with your child's growth or development, they may be referred to a paediatrician (a specialist in treating children and young people).

Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC), where the bile ducts become progressively inflamed and damaged over time, is a rare complication of ulcerative colitis. Bile ducts are small tubes used to transport bile (digestive juice) out of the liver and into the digestive system.

PSC doesn't usually cause symptoms until it's at an advanced stage. Symptoms can include:

  • fatigue (extreme tiredness)
  • diarrhoea 
  • itchy skin
  • weight loss
  • chills
  • a high temperature (fever)
  • yellowing of the skin and the whites of the eyes (jaundice)

There's currently no specific treatment for PSC, although medications can be used to relieve some of the symptoms, such as itchy skin. In more severe cases, a liver transplant may be required.

Toxic megacolon

Toxic megacolon is a rare and serious complication of severe ulcerative colitis, where inflammation in the colon causes gas to become trapped, resulting in the colon becoming enlarged and swollen.

This is potentially very dangerous as it can cause the colon to rupture (split) and cause infection in the blood (septicaemia).

The symptoms of a toxic megacolon include:

  • abdominal (tummy) pain
  • a high temperature (fever)
  • a rapid heart rate

Toxic megacolon can be treated with fluids, antibiotics and steroids given intravenously (directly into a vein). If medications don't improve the conditions quickly then surgical removal of the colon (known as a colectomy) may be needed.

Treating symptoms of ulcerative colitis before they become severe can help prevent toxic megacolon.

Bowel cancer

People who have ulcerative colitis have an increased risk of developing bowel cancer (cancer of the colon, rectum or bowel), especially if the condition is severe or involves most of the colon. The longer you have ulcerative colitis, the greater the risk.

People with ulcerative colitis are often unaware they have bowel cancer as the initial symptoms of this type of cancer are similar. These include:

  • blood in the stools
  • diarrhoea
  • abdominal pain

Therefore, you'll usually have regular check-ups to look for signs of bowel cancer from about 10 years after your symptoms first develop.

Check-ups will involve examining your bowel with a colonoscope – a long, flexible tube containing a camera – that's inserted into your rectum. The frequency of the colonoscopy examinations will increase the longer you live with the condition, and will also depend on factors such as how severe your ulcerative colitis is and if you have a family history of bowel cancer. This can vary between every 1 to 5 years.

To reduce the risk of bowel cancer, it's important to

  • eat a healthy, balanced diet including plenty of fresh fruit and vegetables
  • take regular exercise
  • maintain a healthy weight
  • avoid alcohol and smoking

Taking aminosalicylates as prescribed can also help reduce your risk of bowel cancer.

Read more about preventing bowel cancer.

Living with ulcerative colitis

There are a few things you can do to help keep symptoms of ulcerative colitis under control and reduce your risk of complications.

Dietary advice

Although a specific diet isn't thought to play a role in causing ulcerative colitis, some changes to your diet can help control the condition.

For example, you may find it useful to:

  • eat small meals – eating 5 or 6 smaller meals a day, rather than 3 main meals, may help control your symptoms
  • drink plenty of fluids – it's easy to become dehydrated when you have ulcerative colitis, as you can lose a lot of fluid through diarrhoea. Water is the best source of fluids. Avoid caffeine and alcohol as these will make your diarrhoea worse – and fizzy drinks, which can cause flatulence (gas)
  • take food supplements – ask your GP or gastroenterologist if you need food supplements, as you might not be getting enough vitamins and minerals in your diet

Keep a food diary

Keeping a food diary that documents what you eat can also be helpful. You may find you can tolerate some foods while others make your symptoms worse. By keeping a record of what and when you eat, you should be able to identify problem foods and eliminate them from your diet.

However, you shouldn't eliminate entire food groups (such as dairy products) from your diet without speaking to your care team, because you may not get enough of certain vitamins and minerals.

If you want to try a new food, it's best to only try one type a day, as it's then easier to spot foods that cause problems.

Low-residue diet

Temporarily eating a low-residue or low-fibre diet can sometimes help improve symptoms of ulcerative colitis during a flare-up. These diets are designed to reduce the amount and frequency of the stools you pass.

Examples of foods that can be eaten as part of a low-residue diet include:

  • white bread
  • refined (non-wholegrain) breakfast cereals, such as cornflakes
  • white rice, refined pasta and noodles
  • cooked vegetables (but not the peel, seeds or stalks)
  • lean meat and fish
  • eggs

If you're considering trying a low-residue diet, make sure you talk to your care team first.

Stress relief

Although stress doesn't cause ulcerative colitis, successfully managing stress levels may reduce the frequency of symptoms. The following advice may help:

  • exercise – this has been proven to reduce stress and boost your mood; your GP or care team can advise on a suitable exercise plan
  • relaxation techniques – breathing exercises, meditation and yoga are good ways of teaching yourself to relax
  • communication – living with ulcerative colitis can be frustrating and isolating; talking to others with the condition can help (see below)

Emotional impact

Living with a long-term condition that is as unpredictable and potentially debilitating as ulcerative colitis can have a significant emotional impact.

In some cases, anxiety and stress caused by ulcerative colitis can lead to depression. Signs of depression include feeling very down, hopeless and no longer taking pleasure in activities you used to enjoy. If you think you might be depressed, contact your GP for advice.

You may also find it useful to talk to others affected by ulcerative colitis, either face-to-face or via the internet. Crohn's and Colitis UK is a good resource, with details of local support groups and a large range of useful information on ulcerative colitis and related issues.


The chances of a woman with ulcerative colitis becoming pregnant aren't usually affected by the condition. However, infertility can be a complication of surgery carried out to create an ileo-anal pouch.

This risk is much lower if you have surgery to divert the small intestine through an opening in your abdomen (an ileostomy).


The majority of women with ulcerative colitis who decide to have children will have a normal pregnancy and a healthy baby.

However, if you're pregnant or planning a pregnancy you should discuss it with your care team. If you become pregnant during a flare-up, or have a flare-up while pregnant, there's a risk you could give birth early (premature labour) or have a baby with a low birthweight.

For this reason, doctors usually recommend trying to get ulcerative colitis under control before getting pregnant.

Most ulcerative colitis medications can be taken during pregnancy, including corticosteroids, most 5-ASAs and some types of immunosuppressant medication.

However, there are certain medications (such as some types of immunosuppressant) that may need to be avoided as they're associated with an increased risk of birth defects.

In some cases, your doctors may advise you to take a medicine that isn't normally recommended during pregnancy. This might happen if they think the risks of having a flare-up outweigh the risks associated with the medicine.

Last updated:
15 January 2021