IBS causes recurring abdominal pain with changes in bowel habit. It does not damage the bowel or lead to cancer or inflammatory bowel disease. Most people improve with a combination of diet, targeted medicines and, when needed, gut-directed psychological therapy.

What is it?

IBS is a disorder of gut–brain interaction. The bowel looks normal on tests, but the nerves of the gut are more sensitive and the muscles move food along in an irregular way. Signals between the gut and the brain are amplified, so normal amounts of gas or stretching can feel painful.

It is diagnosed when abdominal pain occurs, on average, at least one day a week over three months and is linked to bowel movements or to a change in how often you go or what your stool looks like. It is grouped by the main bowel pattern: constipation, diarrhoea, or mixed.

What can trigger it?

• A previous episode of gastroenteritis (food poisoning) in some people
• Stress and anxiety, which do not cause IBS but can amplify symptoms through the gut–brain connection
• Certain foods, which differ between people
• Hormonal changes, such as around periods
• Poor sleep and low physical activity

Symptoms

• Cramping abdominal pain, often eased by opening the bowels
• Bloating and visible swelling, often worse as the day goes on
• Diarrhoea, constipation, or both alternating
• Urgency, or a feeling of incomplete emptying
• Mucus in the stool (blood is not part of IBS)

Tests

A confident diagnosis can usually be made from your symptoms with a few simple tests, without many investigations. Typical tests are a blood count, a coeliac disease blood test and an inflammation marker. If you have diarrhoea, a stool test for faecal calprotectin helps exclude inflammatory bowel disease. A colonoscopy is needed only when there are warning features or you are older.

Treatment

Understanding the condition is part of the treatment. These steps are usually taken in order:

• First-line diet: regular meals, enough fluid, less caffeine, fizzy drinks, fatty food and sugar-free sweeteners (sorbitol, mannitol). Soluble fibre such as psyllium (ispaghula), increased slowly, helps especially with constipation
• Regular physical activity, which improves symptoms
• Medicines aimed at the main symptom: peppermint oil capsules or antispasmodics for cramps; laxatives for constipation; loperamide for diarrhoea
• A low-FODMAP diet, done with a dietitian and followed by structured reintroduction, if first-line steps are not enough
• Low-dose 'gut-brain' medicines (neuromodulators), which calm gut nerve sensitivity. They are used at much lower doses than for depression and do not mean the pain is in your head
• Gut-directed hypnotherapy or cognitive behavioural therapy, which have good evidence for persistent symptoms

Living with IBS

Symptoms often come and go. Keeping a short food and symptom diary for two weeks can help you and your doctor spot patterns. Avoid cutting out many foods at once, which can harm nutrition and make eating stressful. Change one thing at a time and give it two to four weeks.

Common questions

This leaflet is general information and does not replace advice from your own doctor. Version 1.0, October 2026. Next review October 2028.