Diagnosis of Irritable Bowel Syndrome

How do doctors diagnose IBS?

To diagnose irritable bowel syndrome (IBS), doctors review your symptoms and medical and family history and perform a physical exam. In some cases, doctors may order tests to rule out other health problems.

Review of your symptoms

Your doctor will ask about your symptoms and look for a certain pattern in your symptoms to diagnose IBS. Your doctor may diagnose IBS if you have pain in your abdomen along with two or more of the following symptoms:

• Your pain is related to your bowel movements. For example, your pain may improve or get worse after bowel movements.
• You notice a change in how often you have a bowel movement.
• You notice a change in the way your stools look.

Your doctor will ask how long you’ve had symptoms. Your doctor may diagnose IBS if

• you’ve had symptoms at least once a week in the last 3 months and
• your symptoms first started at least 6 months ago

Your doctor may diagnose IBS even if you’ve had symptoms for a shorter length of time. You should talk to your doctor if your symptoms are like the symptoms of IBS.

Your doctor will also ask about other symptoms. Certain symptoms may suggest that you have another health problem instead of IBS. These symptoms include

• anemia
• bleeding from your rectum
• bloody stools or stools that are black and tarry
• weight loss

Medical and family history

Your doctor will ask about

• a family history of digestive diseases, such as celiac disease, colon cancer, or inflammatory bowel disease
• medicines you take
• recent infections
• stressful events related to the start of your symptoms
• what you eat
• your history of other health problems that are more common in people who have IBS

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 use tests to diagnose IBS. Your doctor may order blood tests, stool tests, and other tests to check for other health problems.

Blood test

A health care professional will take a blood sample from you and send the sample to a lab. Doctors use blood tests to check for conditions other than IBS, including anemia, infection, and digestive diseases.

Stool test

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 testing. Doctors use stool tests to check for blood in your stool or other signs of infections or diseases. Your doctor may also check for blood in your stool by examining your rectum during your physical exam.

Other tests

Doctors may perform other tests to rule out health problems that cause symptoms similar to IBS symptoms. Your doctor will decide whether you need other tests based on

• blood or stool test results
• whether you have a family history of digestive diseases, such as celiac disease, colon cancer, or inflammatory bowel disease
• whether you have symptoms that could be signs of another condition or disease

Other tests may include

• hydrogen breath test to check for small intestinal bacterial overgrowth or problems digesting certain carbohydrates, such as lactose intolerance
• upper GI endoscopy with a biopsy to check for celiac disease
• colonoscopy to check for conditions such as colon cancer or inflammatory bowel disease