Understanding Irritable Bowel Syndrome: Symptoms, Causes, and Remedies

IBS (irritable bowel syndrome) is a common, usually lifelong condition of the digestive system that causes stomach cramps, bloating, diarrhoea and constipation which come and go, and the NHS says diet changes and medicines can often help control the symptoms.¹ Pooled surveys of 423,362 adults put its prevalence at 9.2% on the Rome III criteria (53 studies, 38 countries) and 3.8% on the stricter Rome IV criteria (six studies), with more women affected than men (12.0% against 8.6%).²

Sources checked on 30 October 2026.

What are the symptoms of IBS?

The NHS lists four main symptoms: stomach pain or cramps, usually worse after eating and better after doing a poo; bloating, with a full, swollen tummy; diarrhoea, with watery poo and sometimes a sudden need to go; and constipation, with straining and a feeling of not having emptied the bowels fully.³ IBS can also cause flatulence, mucus in the poo, tiredness, nausea, backache, bladder urgency, bowel incontinence and pelvic pain, with better days and flare-ups.³

What causes IBS?

The exact cause is not known. The NHS says IBS has been linked to food passing through the gut too quickly or too slowly, a bout of gastroenteritis, oversensitivity of the gut, stress and a family history of IBS.¹ The British Society of Gastroenterology's 2021 guideline describes IBS as a disorder of gut-brain interaction rather than a functional gastrointestinal disorder, a reclassification that followed advances in understanding how it arises.⁴

How is IBS diagnosed?

A GP diagnoses IBS from the pattern of symptoms, not from a scan. NICE guideline CG61 says a diagnosis should be considered when someone has had abdominal pain or discomfort, bloating or a change in bowel habit for at least six months, where the pain is relieved by opening the bowels or linked to a change in stool frequency or form, together with at least two of: altered stool passage (straining, urgency or incomplete emptying), bloating or distension, symptoms made worse by eating, and passing mucus.⁵

There is no test for IBS, but the GP will usually arrange a few to rule out other causes: NICE lists a full blood count, an inflammation marker (ESR, plasma viscosity or CRP) and coeliac antibodies, and the NHS adds a stool sample to check for infections and inflammatory bowel disease.^{5, 6} NICE says colonoscopy and other hospital tests are not needed to confirm IBS in people who meet the criteria.^{5, 6} The NHS advises seeing a GP if you think you might have IBS and have had symptoms for more than four weeks.³

What triggers IBS symptoms, and which foods help?

Flare-ups can happen for no obvious reason. When there is a trigger, the NHS says it is most often alcohol, caffeine, spicy or fatty food, stress and anxiety, or regular antibiotic use.³ Triggers differ from person to person, so the NHS asks people to keep a food and symptom diary and avoid what it shows up.⁷

The NHS diet advice for IBS is a healthy, balanced diet; regular meals eaten slowly rather than skipped or rushed; at least 8 to 10 drinks of fluid (around 1.5 litres) a day; no more than three 80 g portions of fresh fruit and three caffeinated drinks a day; and going easy on fatty, spicy or processed food, alcohol and fizzy drinks.⁷ Fibre is not one rule for everyone: for constipation the NHS says to eat more soluble fibre (oats, pulses, carrots, peeled potatoes and linseeds) and drink plenty of water, while for diarrhoea it says to cut down on high-fibre foods such as wholegrains, nuts and seeds.⁷ For bloating, cramps and wind it suggests regular oats, up to a tablespoon of linseeds a day, and avoiding hard-to-digest vegetables such as cabbage, broccoli, beans and onions, and the sweetener sorbitol.⁷

What helps with IBS?

There is no single diet or medicine that works for everyone with IBS, and NICE's first recommendation is self-help: lifestyle, physical activity, diet, symptom-targeted medicines and time to relax.^{5, 7}

• Low FODMAP diet, under a dietitian. If general diet advice has not helped, a GP can refer you to an NHS dietitian, who may recommend a low FODMAP diet: avoiding foods the gut does not break down easily, such as some fruit and vegetables, milk and wheat products.⁸ NICE says an exclusion diet of this kind should only be given by a professional with expertise in dietary management.⁵ Across 13 randomised trials in 944 people, a low FODMAP diet ranked first for overall symptoms, pain, bloating and bowel habit (relative risk of symptoms not improving 0.67 against a habitual diet), though most trials were in hospital clinics.⁹
• Pharmacy medicines for specific symptoms. The NHS says to ask a pharmacist about antispasmodic medicines or peppermint oil for cramps and bloating, loperamide for diarrhoea and laxatives for constipation; NICE says antispasmodics should be taken as required alongside diet and lifestyle advice, and lactulose avoided.^{5, 7} Across 51 randomised trials in 4,644 adults, peppermint oil capsules ranked first for overall symptoms (relative risk of no improvement 0.63) and tricyclic antidepressants second (0.66), but only 13 trials were at low risk of bias.¹⁰
• Prescription medicines from a GP. If pharmacy medicines are not helping, a GP may prescribe an antidepressant such as amitriptyline or citalopram, which the NHS says can ease IBS symptoms, takes a few weeks to work and can cause side effects.⁸
• Talking therapies. If you have had IBS for a long time and other treatments are not helping, a GP may refer you for cognitive behavioural therapy (CBT), or you can self-refer to NHS talking therapies; NICE suggests CBT, hypnotherapy or psychological therapy when symptoms have not responded to medicines after 12 months.^{5, 8} Across 41 randomised trials in 4,072 people, CBT (relative risk of remaining symptomatic 0.61 to 0.62) and gut-directed hypnotherapy (0.67) had the largest evidence base, though the trials' risk of bias was high and the benefit is probably overestimated.¹¹
• A time-limited trial of live cultures. NICE CG61 says people with IBS who choose to try live cultures (probiotics) should take the product at the manufacturer's dose for at least four weeks while monitoring the effect, and the NHS says to try them for a month; the British Society of Gastroenterology says up to 12 weeks, then stop if nothing has changed.^{4, 5, 7} Across 82 randomised trials in 10,332 people, some species and mixtures improved overall symptoms and pain, but certainty was low to very low for almost every comparison, and adverse events in 55 trials were no higher than on placebo.¹²

How do I know if my IBS is serious?

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have lost a lot of weight for no reason, you are bleeding from your bottom or have bloody diarrhoea, you find a hard lump or swelling in your tummy, or you have shortness of breath, palpitations and paler skin than usual; these could be signs of something more serious.³ NICE adds that anyone with possible IBS should be checked for red-flag signs of cancer or inflammatory bowel disease and referred to hospital if any are present.⁵ Also see a GP if diet changes and pharmacy medicines are not helping.⁷

What we don't know

• Which live cultures help whom: only 24 of the 82 probiotic trials were at low risk of bias, and certainty was low to very low for almost every strain.¹²
• How the pharmacy and GP options compare over years: most trials of peppermint oil, antispasmodics and antidepressants ran 4 to 12 weeks.¹⁰
• How a low FODMAP diet works outside hospital clinics, and after foods are reintroduced: the trials rarely studied either.⁹

Frequently asked questions

How long does IBS last?

The NHS says IBS is usually a lifelong problem, with symptoms that come and go and can last for days, weeks or months at a time; the length of flare-ups and quieter spells varies from person to person.^{1, 3}

Can IBS go away on its own?

Symptoms can settle for long stretches, but the NHS describes IBS as usually lifelong, so they can return; diet changes and medicines can often help control them.¹

Where is the pain with IBS?

The NHS describes it as stomach pain or cramps, usually worse after eating and better after doing a poo, and lists backache and pelvic pain among the other symptoms.³

Is IBS caused by food or stress?

Neither on its own. Food and stress are triggers of flare-ups rather than the cause: the NHS lists alcohol, caffeine, spicy or fatty food, stress and anxiety, and regular antibiotic use as common triggers.³

Sources

1. NHS. What is IBS (irritable bowel syndrome). Page last reviewed 17 March 2025. nhs.uk/conditions/irritable-bowel-syndrome-ibs/what-is-ibs.
2. Oka P, et al. Global prevalence of irritable bowel syndrome according to Rome III or IV criteria: a systematic review and meta-analysis. Lancet Gastroenterology & Hepatology, 2020. Systematic review and meta-analysis, 57 cross-sectional surveys, 92 adult populations, 423,362 people; no funding. PubMed 32702295.
3. NHS. Symptoms of IBS (irritable bowel syndrome). Page last reviewed 17 March 2025. nhs.uk/conditions/irritable-bowel-syndrome-ibs/symptoms.
4. Vasant DH, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut, 2021. UK clinical guideline commissioned by the BSG; author interests declared in a supplement. PubMed 33903147.
5. NICE. Irritable bowel syndrome in adults: diagnosis and management (CG61), recommendations 1.1.1.1 to 1.1.2.2 and 1.2.1.1 to 1.2.3.1. Clinical guideline, published 23 February 2008, last updated 4 April 2017. nice.org.uk/guidance/cg61.
6. NHS. Getting diagnosed with IBS (irritable bowel syndrome). Page last reviewed 17 March 2025. nhs.uk/conditions/irritable-bowel-syndrome-ibs/getting-diagnosed.
7. NHS. Diet, lifestyle and medicines for IBS (irritable bowel syndrome). Page last reviewed 17 March 2025. nhs.uk/conditions/irritable-bowel-syndrome-ibs/diet-lifestyle-and-medicines.
8. NHS. Further help and support for IBS (irritable bowel syndrome). Page last reviewed 17 March 2025. nhs.uk/conditions/irritable-bowel-syndrome-ibs/further-help-and-support.
9. Black CJ, et al. Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis. Gut, 2022. Systematic review and network meta-analysis, 13 randomised trials, 944 patients; no competing interests declared. PubMed 34376515.
10. Black CJ, et al. Efficacy of soluble fibre, antispasmodic drugs, and gut-brain neuromodulators in irritable bowel syndrome: a systematic review and network meta-analysis. Lancet Gastroenterology & Hepatology, 2020. Systematic review and network meta-analysis, 51 randomised trials, 4,644 adults, 4 to 12 weeks; 13 trials at low risk of bias; no funding. PubMed 31859183.
11. Black CJ, et al. Efficacy of psychological therapies for irritable bowel syndrome: systematic review and network meta-analysis. Gut, 2020. Systematic review and network meta-analysis, 41 randomised trials, 4,072 adults; high risk of bias; no competing interests declared. PubMed 32276950.
12. Goodoory VC, et al. Efficacy of probiotics in irritable bowel syndrome: systematic review and meta-analysis. Gastroenterology, 2023. Systematic review and meta-analysis, 82 randomised placebo-controlled trials, 10,332 adults with IBS, 24 at low risk of bias; funding not stated on PubMed. PubMed 37541528.

Spotted something out of date? Email support@wellgard.co.uk with the page address and the sentence.

General information, not medical advice. IBS is diagnosed and managed by a GP; ask for an urgent appointment or contact NHS 111 if you have any of the symptoms listed above.