How is irritable bowel syndrome (IBS) diagnosed?

Dr. Jeanne Morrison, PhD
Family Practitioner

If you have some of the characteristic symptoms of irritable bowel syndrome, such as mucus in your stool and bloating, your doctor will first run certain diagnostic tests on you to rule out other disorders. If your results are negative, your doctor may diagnose you with irritable bowel syndrome if your symptoms have the following history and features:

1. You've had abdominal discomfort for at least 12 consecutive or nonconsecutive weeks out of the last year.

2. Your abdominal discomfort has two of these three characteristics:

  • When the discomfort starts, your bowel movement frequency changes.
  • When the discomfort starts, the appearance or form of your bowel movement changes.
  • Your discomfort is relieved when you have a bowel movement.

Healthcare professionals use a symptom checklist called the Rome Criteria to diagnose irritable bowel syndrome (IBS). It requires that people have at least three months of recurrent abdominal pain or discomfort along with two or more of the following:

Abdominal pain or discomfort that is:

  • relieved with defecation
  • associated with a change in frequency of stool
  • associated with a change in form (appearance) of stool

When diagnosing IBS, doctors will also ask if you have these other symptoms:

  • changes in stool frequency (often defined as more than three bowel movements per day or fewer than three bowel movements per week)
  • lumpy/hard or loose/watery stools
  • changes in the passage of stools (straining, urgency or feeling of incomplete evacuation)
  • passage of mucus
  • bloating or feeling of abdominal distension

In addition to taking a complete medical history that includes a careful description of symptoms, your doctor may do one or more of the following:

  • Order lab tests
  • Order a flexible sigmoidoscopy or, for older patients, a colonoscopy
  • Conduct a pelvic exam to rule out ovarian tumors and cysts or endometriosis, which may cause symptoms similar to IBS
  • Test for lactose intolerance
  • Test a stool sample for signs of bleeding
  • Order an imaging test of the bowel and abdomen, such as a computerized tomography (CT) scan or small bowel series
  • Test for gluten allergy, called celiac disease

This content originally appeared on

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.