What are the key diagnostic criteria for Irritable Bowel Syndrome (IBS) in adults according to NICE guidelines?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 14 August 2025Updated: 14 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

A diagnosis of IBS should be considered only if the person has abdominal pain or discomfort that is either relieved by defaecation or associated with altered bowel frequency or stool form .

It should be accompanied by at least 2 of the following 4 symptoms: altered stool passage (straining, urgency, incomplete evacuation), abdominal bloating (more common in women than men), symptoms made worse by eating, and passage of mucus .

Healthcare professionals should assess and exclude 'red flag' indicators such as signs of cancer or inflammatory markers for inflammatory bowel disease, before confirming the diagnosis .

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