Exams and Tests

Irritable bowel syndrome (IBS) can be diagnosed based on symptoms. In most cases, only minimal tests are needed. A health professional diagnoses IBS when a person has the typical symptoms of the disorder and, if needed, tests have ruled out other possible causes.

The amount of testing that may be done depends on several factors: your age, how your symptoms come on and how severe they are, and how you respond to the initial treatment. For example:

• For a 20-year-old woman who has all the typical symptoms of IBS, a routine blood test may be the only test needed. Irritable bowel syndrome is more common in young women, and so if symptoms are typical of IBS, extensive testing is probably not needed.
• For a 55-year-old man whose symptoms started recently, more extensive testing is probably needed. People over age 50 are less likely than younger people to develop IBS symptoms for the first time, so it is more likely that symptoms may be caused by another problem.
• If you get better after some initial treatment for symptoms that the health professional suspects are caused by IBS, no further tests are needed.

Depending on your symptoms, results of the initial tests, or your response to treatment, other tests may be done.

Irritable Bowel Syndrome: Should I Have Tests for IBS Symptoms?

Tests may include:

• Medical history and physical examination.
• A blood test for celiac disease, which may be considered if you have diarrhea as your most common IBS symptom.
• Complete blood count (CBC), which provides information about the kinds and numbers of red blood cells, white blood cells, and platelets in the blood; and sedimentation rate, which checks for inflammation in the body.
• Stool analysis, which may include testing for blood in the stool (fecal occult blood test), infection (stool culture), or parasites (ova and parasites test).

Thyroid function tests and imaging tests, such as colonoscopy, are occasionally done.