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Irritable Bowel Syndrome (IBS)

What is IBS?

Irritable bowel syndrome (IBS) is a disorder that affects your lower GI (gastrointestinal) tract. This includes the small intestine and large intestine (colon). It is diagnosed when a person has belly pain or spasm associated with a change in the appearance or frequency of their bowel movements. It causes:

  • Belly cramps

  • Gas

  • Swelling or bloating

  • Changes in your bowel habits, such as diarrhea or constipation

When you have IBS, your colon looks normal. But it does not work the way it should.

Health experts have not been able to find an exact physical cause for IBS. It is often thought that stress is one cause. Stress may make IBS symptoms worse.

IBS is a long-term, chronic condition. It can be painful. But it doesn’t cause lasting harm to your intestines. And it doesn’t lead to serious disease, such as cancer.

There is no link between IBS and Crohn's disease, ulcerative colitis, or other inflammatory bowel diseases. However, people with inflammatory bowel disease can also have IBS.

What causes IBS?

The exact cause of IBS isn’t known. There are many possible causes of IBS, and they differ from person to person. This means that some people can have the same symptoms but different causes of their IBS. Some experts think that if you have IBS, your colon or small intestine may be more sensitive than normal. That means it has a strong reaction to things that should not normally affect it.

When you have IBS, your colon muscles begin to move and tighten uncontrollably (spasm) after only mild stimulation or after normal events, such as:

  • Eating

  • Swelling or bloating from gas or other material in the colon

  • Some medicines

  • Some foods

Women with IBS seem to have more symptoms during their periods. This could mean that the chemicals (reproductive hormones) released during a woman’s menstrual cycle may increase IBS symptoms.

Some things can make IBS symptoms worse. The two things most likely to make your IBS symptoms worse are the foods you eat and having emotional stress.

  • Diet. Eating makes your colon muscles move or contract. This normally gives you an urge to have a bowel movement 30 to 60 minutes after a meal. Having fat in your diet can cause contractions in your colon after a meal. With IBS, the urge may come sooner. You may also have cramps or diarrhea. Common foods that cause IBS are dairy products with lactose and poorly digested carbohydrates called FODMAPs (fermentable fructans, oligosaccharides, disaccharides, monosaccharides, and polyols).

  • Stress. If you have IBS, stress can make your colon move uncontrollably or spasm. Experts don’t fully understand why. But they believe this happens because the colon is partly controlled by the brain and spinal cord (nervous system). The nervous system controls how your body moves and reacts to things. Going for counseling or therapy and trying to reduce your stress can help to ease IBS symptoms. But this doesn’t mean that IBS is caused by a mental or emotional disorder. IBS is caused in part because of a problem with how the muscles of the colon move.

Who is at risk for IBS?

You are more likely to be at risk for IBS if you:

  • Are young. Most people first get IBS before they are 45 years old.

  • Are a woman. Women get IBS almost twice as often as men.

  • Have had recent gastroenteritis

What are the symptoms of IBS?

Each person’s symptoms may vary. Some of the most common symptoms include:

  • Having belly pain

  • Having painful constipation or diarrhea

  • Going back and forth between having constipation and having diarrhea

  • Having mucus in your stool

The symptoms of IBS may look like other health problems. Always see your healthcare provider to be sure. IBS does not cause rectal bleeding. Discuss any bleeding with your healthcare provider.

How is IBS diagnosed?

Your healthcare provider will look at your past health and give you a physical exam. You may not need any specific testing. Your provider will decide how much testing you need depending on your age and symptoms. They will also do lab tests to check for infection and for redness and swelling (inflammation).

There are usually no physical signs to tell for sure that you have IBS. There are also no exact tests for IBS.

Your healthcare provider will do lab tests and imaging tests to make sure that you don’t have other diseases. These tests may include the following:

  • Blood tests. These are done to see if you are lacking healthy red blood cells (anemia), have an infection, or have an illness caused by inflammation or irritation.

  • Urinalysis and urine culture. These help to see if you have an infection in any part of your urinary system (urinary tract infection or UTI). This includes your kidneys, the tubes that send urine from the kidneys to the bladder (ureters), your bladder, and the urethra, where urine leaves your body.

  • Stool sample for infection. This test checks for any abnormal bacteria or parasites in your digestive tract that may cause diarrhea and other problems. To do this, a small stool sample is taken and sent to a lab. Other infections can also be evaluated by a stool sample. This can be done by stool culture or other methods.

  • Stool testing for blood (fecal immunochemical test). This test checks for hidden blood in your stool that can only be seen with a microscope. A small amount of stool is tested in a lab. If blood is found, it may mean you have redness and swelling (inflammation) in your GI (gastrointestinal) tract.

  • Stool testing for inflammation. Checking stool levels of calprotectin or lactoferrin is common to determine whether your intestine is inflamed.

  • Upper endoscopy, also called esophagogastroduodenoscopy. This test looks at the inside or lining of your food pipe (esophagus), stomach, and the top part of your small intestine (duodenum). This test uses a thin, lighted tube called an endoscope. The tube has a camera at one end. The tube is put into your mouth and throat. Then it goes into your esophagus, stomach, and duodenum. Your healthcare provider can see the inside of these organs. They can also take a small tissue sample (biopsy) if needed.

  • Abdominal X-rays, CT scan or MRI. These tests make images of your internal tissues, bones, and organs. They are not necessary to diagnose IBS. Your provider may order these tests to make sure your symptoms are not caused by certain other problems.

  • Abdominal ultrasound (sonogram). If your symptoms seem like they may be coming from the liver or gallbladder area, an ultrasound can check. It can also check how blood is flowing through different blood vessels.

  • Colonoscopy. This test looks at the full length of your large intestine. It can help check for any abnormal growths, red or swollen tissue (inflammation), sores (ulcers), or bleeding. A long, flexible, lighted tube called a colonoscope is put into your rectum up into the colon. This tube lets your healthcare provider see the lining of your colon and take out a tissue sample (biopsy) to test it. They may also be able to treat some problems that may be found.

  • Breath test. This test may diagnose bacterial overgrowth in the intestines that some believe can lead to IBS.

How is IBS treated?

Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

Treatment for IBS may include:

  • Changes in your diet. Eating a correct diet is important if you have IBS. In some cases, a high-fiber diet can reduce symptoms. Some people get symptoms from lactose and should eat lactose-free dairy products. Some people get symptoms from poorly digestible carbohydrates and fructose. Some people are intolerant to gluten even though they may not have celiac disease. Many people get symptoms from large and fatty meals. Keep a list of foods that cause you pain, and talk about this with your healthcare provider. Also talk with your healthcare provider about FODMAPs and ways to reduce and eliminate them from your diet.

  • Medicines. Your healthcare provider may prescribe fiber supplements or have you take something now and then to loosen your stool (a laxative). Different medicines are used for IBS, depending on your symptoms. They include medicines to prevent constipation, diarrhea, pain, and spasm.

  • Antibiotic. A poorly absorbed antibiotic is used in certain situations to improve IBS symptoms, especially symptoms of bloating, distention, and loose stool.

  • Natural supplements. Some people feel better on various natural supplements called probiotics. Others get relief with peppermint oil capsules. Discuss any use of probiotics with your healthcare provider.

  • Manage stress. Hypnosis, acupuncture, cognitive behavioral therapy, yoga, regular exercise, relaxation, and other mindfulness activities can help some people with IBS.

Good fiber sources may include:


Moderate fiber

High fiber


Whole-wheat bread, granola bread, wheat bran muffins, waffles, popcorn




Whole-wheat cereals

Whole-bran cereals


Beets, broccoli, Brussels sprouts, cabbage, carrots, corn, green beans, green peas, acorn and butternut squash, spinach, potato with skin, avocado




Apples with peel, dates, papayas, mangos, nectarines, oranges, pears, kiwis, strawberries, applesauce, raspberries, blackberries, raisins

Cooked prunes, dried figs

Meat substitutes

Peanut butter, nuts

Baked beans, black-eyed peas, garbanzo beans, lima beans, pinto beans, kidney beans, chili with beans, trail mix

What are possible complications of IBS?

The diarrhea and constipation that happen with IBS can cause hemorrhoids. If you already have hemorrhoids, they may get worse.

Your quality of life may be affected by IBS, as the symptoms may limit your daily activities.

What can I do to prevent IBS?

Health experts don’t know what causes IBS. They also don’t know how to stop it from happening.

Living with IBS

IBS symptoms can affect your daily activities. It’s important to work with your healthcare provider to manage the disease. You may need a plan to deal with issues, such as diet, work, lifestyle, and emotional or mental health.

When should I call my healthcare provider?

Call your healthcare provider right away if your symptoms get worse or if you have new symptoms.

Key points about IBS

  • IBS is a disorder that affects your lower GI tract. This includes the small intestine and large intestine (colon).

  • It is a long-term, chronic disorder.

  • The exact cause of IBS is not known. There are probably many different causes in different people.

  • When you have IBS, your colon looks normal. But it does not work the way it should.

  • The things most likely to make symptoms of IBS worse are diet and emotional stress.

  • Treatment may include changing your diet and taking medicines.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your healthcare provider if you have questions, especially after office hours or on weekends and holidays.

Medical Reviewers:

  • Jen Lehrer MD
  • L Renee Watson MSN RN
  • Raymond Turley Jr PA-C