Quick answer. Ulcerative colitis is a long-term inflammatory bowel disease affecting the colon and rectum, causing bloody diarrhoea, urgency and abdominal cramps. It is managed with medicines that control inflammation, and a severe flare with heavy bloody diarrhoea, fever or a racing heartbeat needs urgent care.
Ulcerative colitis is a type of inflammatory bowel disease (IBD) in which the lining of the colon (large intestine) and rectum becomes inflamed and develops small ulcers. Unlike Crohn’s disease, which can affect any part of the gut, ulcerative colitis is confined to the colon and affects it in a continuous pattern. It is a lifelong condition that tends to flare and then settle into remission.
This guide explains what ulcerative colitis is, how to recognise it, how it differs from Crohn’s disease and IBS, how a gastroenterologist diagnoses it with a colonoscopy, and how flares are treated and managed. It also sets out the warning signs of a severe flare that needs urgent attention.
At a glance
| Feature | Flare (active) | Remission (settled) |
|---|---|---|
| Stools | Frequent, often bloody | Normal or near-normal |
| Urgency | Strong, hard to hold | Minimal |
| Cramps | Common | Few or none |
| Energy | Tired, unwell | Usually back to normal |
| Goal | Settle inflammation | Maintain with medicines |
What is ulcerative colitis?
Ulcerative colitis is a chronic inflammatory bowel disease in which the immune system causes inflammation and tiny ulcers in the inner lining of the colon and rectum. The inflammation is continuous, usually starting at the rectum and extending up the colon to a variable degree.
It often begins in younger adulthood but can start at any age. Like other forms of IBD, it follows a relapsing-remitting course, with periods of active symptoms (flares) and quieter periods (remission). It cannot currently be cured, but treatment can control inflammation and, for most people, keep symptoms in check.
Symptoms & signs
The main symptoms relate to inflammation of the colon and rectum. Common features include:
- Diarrhoea, often containing blood or mucus
- A frequent and urgent need to empty the bowels
- Tummy pain and cramping, often on the left side
- Feeling that the bowel has not fully emptied
- Tiredness and reduced appetite
- Weight loss in more active disease
Some people also have symptoms beyond the gut, such as joint pain, eye inflammation or skin problems, particularly during a flare.
Causes & risk factors
The exact cause is not fully understood. It is thought to involve an overactive immune response in people with a genetic susceptibility, triggered by environmental factors. Factors linked to ulcerative colitis include:
- A family history of inflammatory bowel disease
- Age – it often starts in late teens to thirties
- Differences in gut bacteria and immune response
Ulcerative colitis is not caused by stress or diet, although these can affect how symptoms feel, and it is not contagious. Interestingly, unlike Crohn’s, the condition is less common in current smokers, but smoking is harmful overall and is not recommended as any kind of treatment.
How it's diagnosed
A gastroenterologist confirms ulcerative colitis by examining the colon and ruling out other causes of bloody diarrhoea. Tests usually include:
- Colonoscopy with biopsies – the key test, allowing the doctor to see the inflamed lining and take tissue samples
- Stool tests – to measure bowel inflammation and exclude infection
- Blood tests – for inflammation and anaemia
These tests help distinguish ulcerative colitis from Crohn’s disease (which can affect the whole gut and tends to be patchy) and from IBS (which does not cause inflammation or bleeding).
Treatment options
Treatment aims to settle flares and then keep the disease in remission for as long as possible. Options include:
- Aminosalicylates (5-ASAs) – anti-inflammatory medicines, often the first step
- Steroids – to bring an active flare under control, used short-term
- Immune-modifying medicines – to maintain remission
- Biologic and other advanced therapies – for moderate to severe disease
- Surgery – removing the colon may be considered for severe disease that does not respond, or to remove the risk of certain complications
People with long-standing ulcerative colitis are usually offered regular colonoscopy surveillance because long-term inflammation can raise the risk of bowel cancer.
When to see a doctor & which specialist
See a doctor if you have ongoing diarrhoea with blood or mucus, urgent or frequent bowel movements, persistent cramps or unexplained weight loss, so you can be assessed. Seek urgent care or call 995 if you have a severe flare – heavy or very frequent bloody diarrhoea, a high fever, a fast heartbeat, a swollen painful abdomen or signs of severe dehydration. A severe flare can be dangerous and needs hospital treatment.
Ulcerative colitis is diagnosed and managed by a gastroenterologist. You can find one through our directory of best gastroenterologists in Singapore.
Living well with ulcerative colitis
Between flares, day-to-day habits can make symptoms easier to manage. There is no single “colitis diet”, but many people find it helps to eat regularly, stay well hydrated, and keep a simple food-and-symptom diary to spot anything that consistently upsets them. During an active flare, lighter, lower-fibre meals are sometimes gentler on the bowel; in remission, a varied, balanced diet is usually best. Stopping smoking, moderating alcohol and finding ways to manage stress are all worthwhile, even though stress does not cause the disease. Take your medicines as prescribed and keep up regular vaccinations, as some treatments affect the immune system.
Questions to ask your doctor
- How much of my colon is affected, and how severe is it?
- What should I do if a flare starts at home, and when should I call you?
- Could my treatment affect vaccinations, pregnancy or fertility?
- How often will I need colonoscopy surveillance?
Common questions
Will I need surgery?
Most people manage well with medicines. Surgery is considered mainly for severe disease that does not respond or for certain complications.
Can I use MediSave for my care?
MediSave can help with eligible hospital admissions, day-surgery procedures and screening colonoscopies, within set limits, and MediShield Life helps protect Singapore Citizens and Permanent Residents against large hospital bills. Ask the clinic’s billing team for details.
Related guides
- Best Gastroenterology Clinics in Singapore — our editorial shortlist
- gastroenterology clinics directory
- Diverticulitis
- Pancreatitis
- Crohn's disease
- Coeliac disease
- Keratosis pilaris
Sources
- NHS – Ulcerative colitis
- Mayo Clinic – Ulcerative colitis
- HealthHub Singapore
- SingHealth – Conditions & Treatments
Part of our Digestive, liver & gut guides · Browse all health topics