Irritable Bowel Syndrome (IBS)

Reviewed by Hansa D. Bhargava, MD on September 16, 2020

What Is Irritable Bowel Syndrome (IBS)?

IBS is a mix of belly discomfort or pain and trouble with bowel habits: either going more or less often than normal (diarrhea or constipation) or having a different kind of stool (thin, hard, or soft and liquid). Doctors used to call IBS other names including:

  • IBS colitis
  • Mucous colitis
  • Spastic colon
  • Nervous colon
  • Spastic bowel

There are four types of the condition:

  • IBS with constipation (IBS-C)
  • IBS with diarrhea (IBS-D)
  • Mixed IBS (IBS-M) alternates between constipation and diarrhea
  • Unsubtyped IBS (IBS-U) for people who don't fit into the above types

IBS isn’t life-threatening, and it doesn't make you more likely to get other colon conditions, such as ulcerative colitis, Crohn's disease, or colon cancer. But it can be a long-lasting problem that changes how you live your life. People with IBS may miss work or school more often, and they may feel less able to take part in daily activities. Some people may need to change their work setting: shifting to working at home, changing hours, or even not working at all.

IBS Symptoms

People with IBS have symptoms that can include:

  • Diarrhea (often described as violent episodes of diarrhea)
  • Constipation
  • Constipation alternating with diarrhea
  • Belly pains or cramps, usually in the lower half of the belly, that get worse after meals and feel better after a bowel movement
  • A lot of gas or bloating
  • Harder or looser stools than normal (pellets or flat ribbon stools)
  • A belly that sticks out
  • Mucus in your poop
  • Feeling like you still need to poop after you just did
  • Food intolerance
  • Tiredness
  • Anxiety
  • Depression
  • Heartburn and indigestion
  • Headaches
  • Needing to pee a lot

Other things may cause these symptoms sometimes. If it’s IBS, you’ll likely have these symptoms weekly for 3 months, or less often for at least 6 months. Women with IBS may have more symptoms during their period. Some people also have urinary symptoms or sexual problems. Stress can make symptoms worse.

IBS Causes and Risk Factors

While several things are known to trigger IBS symptoms, experts don't know what causes the condition. IBS affects between 25 million and 45 million Americans. Most of them are women. People are most likely to get the condition in their late teens to early 40s.


Studies suggest that the colon gets hypersensitive, overreacting to mild stimulation. Instead of slow, rhythmic muscle movements, the bowel muscles spasm. That can cause diarrhea or constipation.

Some think that IBS happens when the muscles in the bowels don't squeeze normally, which affects the movement of stool. But studies don’t seem to back this up.

Another theory suggests it may involve chemicals made by the body, such as serotonin and gastrin, that control nerve signals between the brain and digestive tract.

Other researchers are studying to see if certain bacteria in the bowels can lead to the condition.

Because IBS happens in women much more often than in men, some believe hormones may play a role. So far, studies haven’t borne this out.

A small study published in January 2021 suggests that a GI tract infection, such as food poisoning, can change the immune system so that it responds to certain foods as if they're a threat, like germs or viruses. Researchers are looking into these early findings.  

IBS Diagnosis

There are no specific lab tests that can diagnose IBS. Your doctor will see if your symptoms match with the definition of IBS, and they may run tests to rule out conditions such as:

Your doctor may do some of the following tests to decide if you have IBS:

IBS Treatment and Home Care

Nearly all people with IBS can get help, but no single treatment works for everyone. You and your doctor will need to work together to find the right treatment plan to manage your symptoms.

Many things can trigger IBS symptoms, including certain foods, medicines, the presence of gas or stool, and emotional stress. You’ll need to learn what your triggers are. You may need to make some lifestyle changes and take medication.

Diet and lifestyle changes

Usually, with a few basic changes in diet and activities, IBS will improve over time. Here are some tips to help ease symptoms:

  • Avoid caffeine (in coffee, tea, and soda).
  • Add fiber to your diet with foods like fruits, vegetables, whole grains, and nuts.
  • Drink at least three to four glasses of water per day.
  • Don't smoke.
  • Learn to relax, either by getting more exercise or by reducing stress in your life.
  • Limit how much milk or cheese you eat.
  • Eat smaller meals more often instead of big meals.
  • Keep a record of the foods you eat so you can figure out which foods bring on bouts of IBS.


Common food "triggers" are red peppers, green onions, red wine, wheat, and cow's milk. If you're concerned about getting enough calcium, you can try to get it from other foods, like broccoli, spinach, turnip greens, tofu, yogurt, sardines, salmon with bones, calcium-fortified orange juice and breads, or calcium supplements.


The following types of drugs are used to treat IBS:

  • Bulking agents, such as psyllium, wheat bran, and corn fiber, help slow the movement of food through the digestive system and may also help relieve symptoms.
  • Antibiotics, such as rifaximin (Xifaxan), can change the amount of bacteria in your intestines. You take pills for 2 weeks. It can control symptoms for as long as 6 months. If they come back, you can be treated again.

Other treatments can help with symptoms of IBS:

Belly pain and bloating

  • Antispasmodics can control colon muscle spasms, but experts are unsure that these drugs help. They also have side effects, such as making you drowsy and constipated, that make them a bad choice for some people.
  • Antidepressants may also help relieve symptoms in some people.
  • Probiotics, which are live bacteria and yeasts that are good for your health, especially your digestive system; doctors often suggest them to help with digestive problems.



  • Linaclotide (Linzess) is a capsule you take once daily on an empty stomach, at least 30 minutes before your first meal of the day. It helps to relieve constipation by helping bowel movements happen more often. It’s not for anyone 17 years old or younger. The drug's most common side effect is diarrhea.
  • Lubiprostone (Amitiza) can treat IBS with constipation in women when other treatments have not helped. Studies haven’t fully shown that it works well in men. Common side effects include nausea, diarrhea, and belly pain. More serious side effects may include fainting, swelling of the arms and legs, breathing problems, and heart palpitations.
  • Plecanatide (Trulance) has been shown to treat constipation without the usual side effects of cramping and belly pain. The once-a-day pill can be taken with or without food. It works to increase gastrointestinal fluid in your gut and encourage regular bowel movements.
  • Polyethylene glycol (PEG) is an osmotic laxative and causes water to remain in the stool, which results in softer stools. This medication may work best for those who can't tolerate dietary fiber supplements.
  • Tegaserod is a drug for women. It works by speeding up the motion in your gut. This effect shortens the time stool remains in the bowel, and helps lessen symptoms such as belly pain and constipation.
  • Tenapanor (IBSRELA) increases bowel movements and decreases belly pain.



  • Alosetron (Lotronex) can help relieve stomach pain and slow your bowels to relieve diarrhea, but there can be serious side effects, so it’s only to be used by women with severe IBS-D whose symptoms aren’t helped by other treatments.
  • Bile acid sequestrants are cholesterol-lowering medications. Taken orally, they work in the intestines by binding bile acids and reducing stool production.
  • Eluxadoline (Viberzi) is prescribed to help reduce bowel contractions, belly cramps, and diarrhea.
  • Loperamide (Imodium) works by slowing down the movement of the gut. This decreases the number of bowel movements and makes the stool less watery.

Make sure to follow your doctor's instructions when taking IBS medications, including laxatives, which can be habit-forming if you don’t use them carefully.

WebMD Medical Reference



National Digestive Diseases Information Clearinghouse.

Irritable Bowel Syndrome Association.


National Institute of Diabetes and Digestive and Kidney Diseases: “Irritable Bowel Syndrome (IBS).” “Is it food intolerance?”

Nature: "Local immune response to food antigens drives meal-induced abdominal pain."

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