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Irritable Bowel Syndrome (IBS)

Medically reviewed by Last updated on Jan 2, 2024.

What is Irritable Bowel Syndrome (IBS)?

Harvard Health Publishing

Irritable bowel syndrome (IBS) is a common disorder that causes a variety of symptoms, including:

Irritable Bowel Syndrome (IBS)

The severity of the disorder varies from person to person. Some people experience symptoms that come and go and are just mildly annoying. Others have such severe daily bowel problems that IBS affects their ability to work, sleep and enjoy life.  

In addition, symptoms may change over time. A person may have severe symptoms for several weeks and then feel well for months or even years.  

Most people are never cured of IBS. However, the disorder is not related to any other disease. It does not develop into colitis. People with IBS do not have an increased risk of colon cancer

IBS usually starts in early adulthood. It affects twice as many women as men. Approximately 10% to 20% of the population has IBS. But half of all people with the condition never seek medical care for their symptoms.  

No one knows what causes IBS. Some studies suggest that the nerves of the colon may be much more sensitive than usual in people with IBS. The normal movement of food and gas through the colon causes pain, intestinal spasms and an irregular pattern of bowel movements. 

Stress does not cause IBS. But stress can increase the frequency and severity of symptoms. 

IBS has been called irritable colon, spastic colon, mucous colitis and functional bowel disease. 


People with IBS may have some or all of these symptoms:  

Although the symptoms of IBS often change over time, people tend to develop their own pattern. For example, some people have mostly diarrhea, some have mostly constipation and others have abdominal pain without a major change in bowel movements.


There is no test for IBS. Your doctor will diagnose IBS if you have the typical symptoms and have been tested for other disorders that can cause similar symptoms.  

Your doctor will ask about your medical history and symptoms. Your doctor will examine you, testing your abdomen for tenderness and feeling to determine whether internal organs are larger than normal. The doctor will check for fever or weight loss. If you have any of these signs, you likely have something other than IBS. 

Depending on your medical history, your doctor may do tests to eliminate other diseases that may cause similar symptoms. These tests might include:  

Your doctor may suggest that you stop eating or drinking certain foods for up to three weeks to determine if your diet is contributing to your symptoms. For example, your doctor may ask you to eliminate milk products if he or she suspects lactose intolerance.  

Expected Duration

IBS symptoms may be a daily problem throughout a person's life. Symptoms may come and go, lasting a day, a week or a month before disappearing. Dietary changes with or without medication may help to reduce the frequency or severity of symptoms. 


Because no one knows what causes IBS, it is impossible to prevent the disorder. Once diagnosed with IBS, a person may be able to reduce the frequency and severity of symptoms by reducing stress or changing the diet. 


Changing your diet may improve symptoms dramatically. It often takes a long time to discover what works well for you. And you may need to alter your original program if symptoms flare.  

Keep track of the different foods you eat throughout the day. See which foods seem to make your symptoms worse. After you discover your particular trigger foods, eliminate them from your diet. Some common IBS trigger foods include:  

The way you eat may help to create IBS symptoms. Eating large meals can cause cramping and diarrhea, so eating smaller meals more often may help some people with IBS. Eating quickly can cause you to swallow air, which can cause belching or gas. 

Adding fiber to your diet, especially if constipation is one of your main symptoms, often helps to regulate your bowel movements and reduce abdominal discomfort. At first, fiber will increase the amount of gas in your system, so add fiber gradually. Over time, the body adjusts to the effects of fiber and the gassiness will decrease. Fruits, vegetables and whole grain breads and cereals are good food sources of fiber.  

Your doctor may recommend a fiber supplement. Some experts believe that the fiber methylcellulose creates the least amount of gas, and brands of this fiber are often recommended for people with IBS. Psyllium is also a good source of fiber.  

If your symptoms are not relieved after you eliminate trigger foods and add fiber, your doctor may prescribe medications.  

For people that have frequent loose stools (diarrhea-predominant IBS), medication options include:  

For people with constipation-predominant IBS, fiber and plenty of fluids are the mainstays of therapy. If medication is needed, your doctor may prescribe an osmotic laxative such as lactulose.  

Other drugs available for constipation predominant irritable bowel syndrome include: 

Both drugs act on the cells that line the inside of the intestines. They promote increased fluid secretion into the intestine, making stool passage easier. 

Treatment options

The following list of medications are in some way related to or used in the treatment of this condition.

View more treatment options

When To Call a Professional

When To Call a Professional 

It is useful for anyone with irritable bowel symptoms to discuss their symptoms with a doctor, so that diet, fiber and drug treatment strategies can be planned. 

After you have been diagnosed with irritable bowel syndrome, contact your doctor if you have: 


There is no cure for IBS. But most people can lessen the symptoms by making dietary changes, reducing stress and, if necessary, taking medication.

Additional Info

National Institute of Diabetes & Digestive & Kidney Disorders

American College of Gastroenterology (ACG)

American Gastroenterological Association

Learn more about Irritable Bowel Syndrome

Treatment options

Care guides guides (external)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.