Diagnosis of Irritable Bowel Syndrome

How do doctors diagnose IBS?

Your doctor may be able to diagnose irritable bowel syndrome (IBS) based on a review of your medical history, symptoms, and physical exam. Your doctor may also order tests.

To diagnose IBS, your doctor will take a complete medical history and perform a physical exam.

Medical History

The medical history will include questions about

Doctor talking to patient
  • your symptoms
  • family history of gastrointestinal (GI) tract disorders
  • recent infections
  • medicines
  • stressful events related to the start of your symptoms

Your doctor will look for a certain pattern in your symptoms. Your doctor may diagnose IBS if

  • your symptoms started at least 6 months ago
  • you’ve had pain or discomfort in your abdomen at least three times a month for the past 3 months
  • your abdominal pain or discomfort has two or three of the following features:
    • Your pain or discomfort improves after a bowel movement.
    • You notice a change in how often you have a bowel movement.
    • You notice a change in the way your stools look.

Physical Exam

During a physical exam, your doctor usually

  • checks for abdominal bloating
  • listens to sounds within your abdomen using a stethoscope
  • taps on your abdomen checking for tenderness or pain

What tests do doctors use to diagnose IBS?

In most cases, doctors don’t need to perform tests to diagnose IBS. Your doctor may perform a blood test to check for other conditions or problems. Your doctor may perform more tests based on the results of the blood test and if you have

Blood test

Doctors use blood tests to check for conditions or problems other than IBS. A health care professional sends your blood sample to a lab.

Stool test

A stool test is the analysis of a sample of stool. Your doctor will give you a container for catching and holding a stool sample. You will receive instructions on where to send or take the kit for analysis, to check for blood or parasites. Your doctor may also check for blood in your stool by examining your rectum during your physical exam.

Flexible sigmoidoscopy

Flexible sigmoidoscopy is a procedure that uses a flexible, narrow tube with a light and tiny camera (called a sigmoidoscope) on one end to look inside your rectum and lower colon.

This procedure can show signs of conditions or problems in the lower GI tract. During the procedure, the doctor can take a biopsy. You won’t feel the biopsy.


Colonoscopy is a procedure that uses a long, flexible, narrow tube with a light and tiny camera (called a colonoscope) on one end to look inside your rectum and colon.

Colonoscopy can show irritated or swollen tissue, ulcers, polyps, and cancer. A trained specialist performs this procedure.

Colonoscopy testing and colon description
Colonoscopy testing
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Lower GI series

A lower GI series, also called a Barium Enema, uses x-rays to look at your large intestine.

During a lower GI series, you’ll be asked to lie on a table while the doctor inserts a flexible tube into your anus. The doctor will fill your large intestine with barium. You may be asked to change positions several times during the test.

February 2015

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.