Overview
Irritable bowel syndrome is a common gut disorder causing recurrent abdominal pain or discomfort linked to bowel habit changes, without structural or biochemical abnormalities. It is a functional disorder, meaning the gut functions abnormally despite appearing normal on tests. IBS is chronic but not dangerous and does not increase cancer risk.
How common is it?
IBS is a common digestive condition. Symptoms vary over time and can substantially affect daily life.
Causes and risk factors
IBS results from disturbed gut-brain communication, altered gut motility, visceral hypersensitivity, and in some cases changes in the gut microbiome.
Common risk factors
- Previous gastroenteritis can be associated with the onset of IBS
- Gut-brain axis dysregulation and heightened pain sensitivity
- Altered gut motility (too fast or too slow)
- Gut microbiome changes
- Psychological factors: anxiety, depression, and adverse life events
- FODMAP intolerance (fermentable carbohydrates)
- Female sex hormones (flares common with menstruation)
- Family history
Symptoms
- Recurrent abdominal pain or discomfort, typically relieved by defecation
- Bloating and distension
- Diarrhoea (IBS-D), constipation (IBS-C), or alternating (IBS-M)
- Mucus in the stool
- Urgency to defecate
- Feeling of incomplete emptying
- Worsening with stress or particular foods
When to see a doctor
Seek urgent medical advice for rectal bleeding, bloody diarrhoea, unexplained weight loss, a hard abdominal lump or symptoms of anaemia such as breathlessness and unusual pallor. Arrange assessment for a new or changing bowel pattern, especially after age 50 or with a family history of bowel cancer, coeliac disease or IBD.
Diagnosis
IBS is diagnosed clinically using the Rome IV criteria, after excluding other causes. Blood tests (FBC, CRP, coeliac antibodies), faecal calprotectin to exclude IBD, and colonoscopy if red flags are present.
Treatments
Low-FODMAP diet
Reducing fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (found in wheat, onion, garlic, apples, lactose, and artificial sweeteners) significantly improves symptoms in 50 to 75% of patients. Should be supervised by a dietitian.
Antispasmodics
Mebeverine, hyoscine, or peppermint oil capsules reduce abdominal pain and spasm. Taken before meals or at onset of symptoms.
Laxatives and antidiarrhoeals
Ispaghula husk or laxatives for constipation-predominant IBS; loperamide for diarrhoea-predominant IBS.
Gut-directed psychological therapies
Cognitive behavioural therapy (CBT) and gut-directed hypnotherapy are as effective as drug treatment and produce lasting improvement, especially for anxiety-linked IBS.
Low-dose antidepressants
A clinician may consider a low-dose tricyclic antidepressant or, in selected cases, an SSRI when other measures have not helped. These medicines may affect gut pain signalling; choice and dose require review of symptoms, side effects and other medicines.
Self-care and lifestyle
- Eat regular meals and do not skip breakfast
- Limit fresh fruit to 3 portions per day
- Reduce caffeine, alcohol, and fizzy drinks
- Incorporate 30 minutes of aerobic exercise most days (proven to reduce IBS symptoms)
- Stress management and relaxation techniques
Prevention
There is no proven way to prevent IBS. Regular meals, physical activity and managing stress may help symptoms. Antibiotics should not be taken to prevent IBS; a clinician should decide whether an infection needs antibiotic treatment.
Sources for targeted updates
Updated: 24 October 2026. Specific treatment, safety or key-fact statements corrected in this update; further corrections to frequency, risk factors, urgent-care guidance. This update covers the named sections; a full review of the remaining guide is pending.