How to Know if You Have Irritable Bowel Syndrome

Medically Reviewed by Melinda Ratini, DO, MS on July 20, 2021

Your stomach has been feeling crummy for a while now. That pain and cramping comes and goes, but even after a few months, you just can't shake it. You've heard of something called IBS -- or irritable bowel syndrome. Could it be what you've got? And how will your doctor find out?

There are some tests that help figure out what's going on, including a new blood test. But the most common way your doctor makes a diagnosis is with a bit of detective work.

Identify Your Symptoms

Your doctor will ask for the details of what's bothering you. They'll compare that with a set of symptoms known as the Rome IV Criteria. 

To meet the standard, your belly pain needs to have been a problem for at least 6 months. And in the last 3 months, you'll have noticed it at least 1 day per week. 

You also need to have two of these symptoms:

  • Your belly pain is related to a bowel movement.
  • When you have pain or discomfort, your bowel movements are either more or less frequent than usual.
  • Your stools have changed in appearance and are harder or softer than usual when you have pain or discomfort.

Your doctor will also want to know if you feel better after a bowel movement. This is another sign of IBS. It can be hard to remember all your symptoms. Your doctor may ask you to write down what you notice on a calendar or in a notebook.

Your doctor may also ask you to change your diet to see if that helps. Some people can't digest lactose, a natural sugar found in dairy products. This is called lactose intolerance. It can cause many of the same things IBS does, like belly pain, gas, and diarrhea. It may help if you:

  • Stay away from dairy, including cheese, milk, yogurt, and sour cream, for a while to see if you feel better.
  • Try something called a low FODMAP diet that cuts down on hard-to-digest carbs such as wheat, beans, and certain fruits and vegetables and limits dairy.
  • Eat small and more frequent meals.
  • Use probiotics.

If you have the symptoms of IBS and a different diet doesn’t help -- and you don't have any red flags for another disease, like blood in your stool, unexplained weight loss, or fever to explain your symptoms -- your doctor may not need to check further. They may be ready to diagnose you with IBS and start treatment.

But if your symptoms include a change in bowel habits, or if they only started after you turned 50, you may need tests to look for other possible causes. And if you have a family history of other stomach or intestinal diseases, your doctor will want to rule those out.

Blood Test for IBS

There is no definitive diagnostic laboratory test for IBS. The purpose of laboratory testing is primarily to exclude an alternative diagnosis.

Typically, a complete blood count will be done.  This will check for anemia, infection, or some other bowel diseases.

Tests for Other Diseases

Your doctor has some other ways to see why you're not feeling so great. Sometimes other conditions are to blame. There are tests that can help rule them in or out.

For instance, they may check to see if your body isn't able to absorb or digest certain ingredients, like dairy or a simple sugar called fructose. One way to find out is to see if your symptoms get better if you take them out of your diet.

You may also need to get a blood test to look for signs of Celiac disease, which happens when your body can't handle gluten, a protein found in wheat, barley, and oats.

Your doctor might order a colonoscopy, an exam that looks for polyps in your large intestine. Another option may be a test called a flexible sigmoidoscopy. During both procedures, your doctor puts a narrow, flexible tube with a camera into your rectum. They move it into your body to examine part or all of the large intestine.

During the colonoscopy, they may collect small sections of tissue from the large intestine and examine them under a microscope. It won't show if you have IBS, but you may learn if you've got other conditions like colitis or inflammatory bowel disease.

Another way your doctor might want to look at your large intestine is with an X-ray called a lower GI series, or barium enema. For this test, they put a flexible tube into the rectum and fills the large intestine with barium, a liquid that lights up on X-rays.

Finally, you may be asked to save a stool sample to be tested for blood, infection, or parasites. Your doctor will give you a container and instructions on where to send or take the kit for analysis.

All this testing can seem like a nuisance, but it's vital if you want to find out what's causing your stomach problems. Once you've got a diagnosis, your doctor can start the right treatment and put you on the road to relief.

WebMD Medical Reference



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