Diagnosis and further tests for Irritable Bowel Syndrome (IBS)
Current medical guidelines1 recommend diagnosing irritable bowel syndrome (IBS) based on a person’s symptoms, using established diagnostic criteria known as the Rome criteria, while avoiding unnecessary tests. In most cases, extensive investigations or complex tests are not needed if the symptoms fit the typical pattern of the condition and there are no warning signs or red flags.
However, the clinical assessment may be supported by:
Blood tests. These can help rule out anaemia, identify signs of inflammation and screen for coeliac disease.
When diarrhoea is the predominant symptom, additional tests may be carried out, including:
Stool tests. These tests can help rule out gastrointestinal infections and may include testing for faecal calprotectin. Faecal calprotectin is a marker that can help distinguish IBS from inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis.
Colonoscopy. This test is generally reserved for the following situations:
- A family history of inflammatory bowel disease (IBD) or colorectal cancer.
- Onset of symptoms after the age of 50.
- Unexpected weight loss.
- Presence of blood in the stools.
- Anaemia.
- Nocturnal diarrhoea.
- Raised faecal calprotectin levels.
Bibliography
- Corsetti M, Shin A, Lacy BE, Cash BD, Simren M, Schmulson MJ, Hou X, Lembo A, BOWEL DISORDERS, Gastroenterology (2026), doi: https://doi.org/10.1053/ j.gastro.2026.02.003.
Substantiated information by:
Published: 25 September 2026
Updated: 25 September 2026
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