There are no definitive tests for Irritable Bowel Syndrome (IBS). Diagnosis is usually done based on the frequency or severity of a patient’s symptoms.

Tests may be run to rule out conditions that can cause symptoms similar to IBS. This is especially important in patients over 50 who are experiencing IBS-like symptoms for the first time. These tests may include:

  • Complete blood count (CBC): A blood test to check for inflammation and blood loss
  • Stool analysis: Stool is examined for the presence of blood, parasites, bacteria, fungus and viral infections
  • Colonoscopy: Looks for growths, tumors, ulcer or narrowing in the large intestine. After you are sedated, the doctor inserts a long, flexible device with a light attached to a video monitor into your rectum to view the entire large intestine.
  • Thyroid function tests: Done to test the thyroid; may be a blood test, x-ray or ultrasound depending on whether the doctor wants to check levels or examine the gland itself
  • Blood tests for celiac disease: Looks for three specific antibodies that are markers for celiac disease: anti-gliadin, anti-tissue transglutaminase, and endomysial
  • Small intestinal biopsy: Looks for loss of villi and increased white blood cells which are characteristic of celiac disease. The doctor inserts a long, flexible device through the mouth and into the duodenum. A long biopsy tool is passed through a channel in the endoscope to take snips of the duodenal lining.