To diagnose irritable bowel syndrome (IBS), doctors typically review a patient’s symptoms, medical and family history, and perform a physical exam. A key part of the diagnosis involves identifying patterns in symptoms, such as abdominal pain linked to bowel movements, changes in stool frequency, and stool appearance. The doctor may diagnose IBS if symptoms have been present at least once a week for the past three months and first started at least six months ago. Additional symptoms such as anemia, rectal bleeding, bloody stools, or weight loss may suggest another condition rather than IBS. During a physical exam, doctors check for abdominal bloating, listen to abdominal sounds, and tap the abdomen to check for tenderness.

While IBS is generally diagnosed based on symptoms, doctors may order tests to rule out other health problems. Blood tests can check for anemia, infection, or other digestive diseases, while stool tests help detect blood or infections. Additional tests, such as a hydrogen breath test, upper GI endoscopy, or colonoscopy, may be used if there are concerns about other conditions like small intestinal bacterial overgrowth, celiac disease, or colon cancer. These tests help ensure that IBS is the correct diagnosis and rule out any other potential causes for the symptoms.

Reference: Diagnosis of Irritable Bowel Syndrome. NIDDK. Updated November 2017. Accessed February 7, 2025. https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome/diagnosis