Irritable Bowel Syndrome: A Comprehensive Overview

Definition & Facts 

What is IBS? 

Irritable bowel syndrome (IBS) is a group of symptoms that occur together, including repeated pain in your abdomen and changes in your bowel movements, which may be diarrhea, constipation, or both. With IBS, you have these symptoms without any visible signs of damage or disease in your digestive tract. 

IBS is a functional gastrointestinal (GI) disorder. Functional GI disorders, which doctors now call disorders of gut-brain interactions, are related to problems with how your brain and your gut work together. These problems can cause your gut to be more sensitive and change how the muscles in your bowel contract. If your gut is more sensitive, you may feel more abdominal pain and bloating. Changes in how the muscles in your bowel contract lead to diarrhea, constipation, or both. 

Does IBS have another name? 

In the past, doctors called IBS colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel. 

Are there different types of IBS? 

Three types of IBS are based on different patterns of changes in your bowel movements or abnormal bowel movements. Sometimes, it is important for your doctor to know which type of IBS you have. Some medicines work only for some types of IBS or make other types worse. Your doctor might diagnose IBS even if your bowel movement pattern does not fit one particular type. 

Many people with IBS have normal bowel movements on some days and abnormal bowel movements on other days. 

IBS with constipation (IBS-C) 

With IBS-C, on days when you have at least one abnormal bowel movement 

  • More than a quarter of your stools are hard or lumpy and 
  • Less than a quarter of your stools are loose or watery 

IBS with diarrhea (IBS-D) 

In IBS-D, on days when you have at least one abnormal bowel movement 

  • More than a quarter of your stools are loose or watery and 
  • Less than a quarter of your stools are hard or lumpy 

IBS with mixed bowel habits (IBS-M) 

In IBS-M, on days when you have at least one abnormal bowel movement 

  • More than a quarter of your stools are hard or lumpy and 
  • More than a quarter of your stools are loose or watery 

How common is IBS? 

Studies suggest that about 12 percent of people in the United States have IBS. 

Who is more likely to develop IBS? 

Women are up to two times more likely than men to develop IBS. People younger than age 50 are more likely to develop IBS than people older than age 50. 

Factors that can increase your chance of having IBS include: 

  • Having a family member with IBS 
  • A history of stressful or difficult life events, such as abuse, in childhood 
  • Having a severe infection in your digestive tract 

What other health problems do people with IBS have? 

People with IBS often have other health problems, including 

  • Certain conditions that involve chronic pain, such as fibromyalgia, chronic fatigue syndrome and chronic pelvic pain 
  • Certain digestive diseases, such as dyspepsia and gastroesophageal reflux disease 
  • Certain mental disorders, such as anxiety, depression, and somatic symptom disorder 

Symptoms & Causes 

What are the symptoms of IBS? 

The most common symptoms of irritable bowel syndrome (IBS) are pain in your abdomen, often related to your bowel movements, and changes in your bowel movements. These changes may be diarrhea, constipation, or both, depending on what type of IBS you have. 

Other symptoms of IBS may include 

  • Bloating 
  • The feeling that you haven’t finished a bowel movement 
  • Whitish mucus in your stool 

Women with IBS often have more symptoms during their periods. 

IBS can be painful but doesn’t lead to other health problems or damage your digestive tract. 

To diagnose IBS, you doctor will look for a certain pattern in your symptoms over time. IBS is a chronic disorder, meaning it lasts a long time, often years. However, the symptoms may come and go. 

What causes IBS? 

Doctors aren’t sure what causes IBS. Experts think that a combination of problems may lead to IBS. Different factors may cause IBS in different people. 

Functional gastrointestinal (GI) disorders such as IBS are problems with brain-gut interaction—how your brain and gut work together. Experts think that problems with brain-gut interaction may affect how your body works and cause IBS symptoms. For example, in some people with IBS, food may move too slowly or too quickly through the digestive tract, causing changes in bowel movements. Some people with IBS may feel pain when a normal amount of gas or stool is in the gut. 

Certain problems are more common in people with IBS. Experts think these problems may play a role in causing IBS. These problems include 

  • Stressful or difficult early life events, such as physical or sexual abuse 
  • Certain mental disorders, such as depression, anxiety, and somatic symptom disorder 
  • Bacterial infections in your digestive tract 
  • Small intestinal bacterial overgrowth, an increase in the number or a change in the type of bacteria in your small intestine 
  • Food intolerances or sensitivities, in which certain foods cause digestive symptoms 

Research suggests that genes may make some people more likely to develop IBS. 


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 


How do doctors treat IBS? 

Doctors may treat irritable bowel syndrome (IBS) by recommending changes in what you eat and other lifestyle changes, medicines, probiotics, and mental health therapies. You may have to try a few treatments to see what works best for you. Your doctor can help you find the right treatment plan. 

Changes to what you eat and other lifestyle changes 

Changes in what you eat may help treat your symptoms. Your doctor may recommend trying one of the following changes: 

  • Eat more fiber 
  • Avoid gluten 
  • Follow a special eating plan called the low FODMAP diet 

Research suggests that other lifestyle changes may help IBS symptoms, including 

  • Increasing your physical activity 
  • Reducing stressful life situations as much as possible 
  • Getting enough sleep 


Your doctor may recommend medicine to relieve your IBS symptoms. 

To treat IBS with diarrhea, your doctor may recommend 

  • Loperamide 
  • Rifaximin (Xifaxan), an antibiotic 
  • Eluxadoline (Viberzi) 
  • Alosetron (Lotronex), which is prescribed only to women and is prescribed with special warnings and precautions 

To treat IBS with constipation, your doctor may recommend 

  • Fiber supplements, when increasing fiber in your diet doesn’t help 
  • Laxatives 
  • Lubiprostone (Amitiza) 
  • Linaclotide (Linzess) 
  • Plecanatide (Trulance) 

Other medicines may help treat pain in your abdomen, including 

  • Antispasmodics 
  • Antidepressants, such as low doses of tricyclic antidepressants and selective serotonin reuptake inhibitors 
  • Coated peppermint oil capsules 

Follow your doctor’s instructions when you use medicine to treat IBS. Talk with your doctor about possible side effects and what to do if you have them. 


Your doctor may also recommend probiotics. Probiotics are live microorganisms, most often bacteria, that are similar to microorganisms you normally have in your digestive tract. Researchers are still studying the use of probiotics to treat IBS. Depending on the type of IBS, there’s a chance that probiotics could make your symptoms worse.  

To be safe, talk with your doctor before using probiotics or any other complementary or alternative medicines or practices. If your doctor recommends probiotics, talk with him or her about how much probiotics you should take and for how long. 

Mental health therapies 

Your doctor may recommend mental health therapies to help improve your IBS symptoms. Therapies used to treat IBS include 

  • Cognitive behavioral therapy, which focuses on helping you change thought and behavior patterns to improve IBS symptoms 
  • Gut-directed hypnotherapy, in which a therapist uses hypnosis—a trance-like state in which you are relaxed or focused—to help improve your IBS symptoms 
  • Relaxation training, which can help you relax your muscles or reduce stress 

Eating, Diet, & Nutrition 

How can my diet help treat the symptoms of IBS? 

Your doctor may recommend changes in your diet to help treat symptoms of irritable bowel syndrome (IBS). Your doctor may suggest that you 

  • Eat more fiber 
  • Avoid gluten 
  • Follow a special diet called the low FODMAP diet 

Different changes may help different people with IBS. You may need to change what you eat for several weeks to see if your symptoms improve. Your doctor may also recommend talking with a dietitian. 

Eat more fiber 

Fiber may improve constipation in IBS because it makes stool soft and easier to pass. The 2015-2020 Dietary Guidelines for Americans recommends that adults should get 22 to 34 grams of fiber a day. 

Two types of fiber are 

  • Soluble fiber, which is found in beans, fruit, and oat products 
  • Insoluble fiber, which is found in whole-grain products and vegetables 

Research suggests that soluble fiber is more helpful in relieving IBS symptoms. 

To help your body get used to more fiber, add foods with fiber to your diet a little at a time. Too much fiber at once can cause gas, which can trigger IBS symptoms. Adding fiber to your diet slowly, by 2 to 3 grams a day, may help prevent gas and bloating. 

Avoid gluten 

Your doctor may recommend avoiding foods that contain gluten—a protein found in wheat, barley, and rye—to see if your IBS symptoms improve. Foods that contain gluten include most cereal, grains, and pasta, and many processed foods. Some people with IBS have more symptoms after eating gluten, even though they do not have celiac disease. If you have not been tested for celiac disease, it’s not recommended to start a gluten-free diet until this testing is complete. 

Low FODMAP diet 

Your doctor may recommend that you try a special diet—called the low FODMAP diet—to reduce or avoid certain foods that contain carbohydrates that are hard to digest. These carbohydrates are called FODMAPs. 

Examples of foods that contain FODMAPs include 

  • Fruits such as apples, apricots, blackberries, cherries, mango, nectarines, pears, plums, and watermelon, or juice containing any of these fruits 
  • Canned fruit in natural fruit juice, or large amounts of fruit juice or dried fruit 
  • Vegetables such as artichokes, asparagus, beans, cabbage, cauliflower, garlic and garlic salts, lentils, mushrooms, onions, and sugar snap or snow peas 
  • Dairy products such as milk, milk products, soft cheeses, yogurt, custard, and ice cream 
  • Wheat and rye products 
  • Honey and foods with high-fructose corn syrup 
  • Products, including candy and gum, with sweeteners ending in “–ol,” such as sorbitol, mannitol, xylitol, and maltitol 

Your doctor may suggest that you try the low FODMAP diet for a few weeks to see if it helps with your symptoms. If your symptoms improve, your doctor may recommend slowly adding foods that contain FODMAPs back into your diet. You may be able to eat some foods with FODMAPs without having IBS symptoms. Before starting a low FODMAP diet, reach out to your dietitian for complete instructions. They will support you through the elimination and reintroduction phases and help personalize the diet to your symptoms and preferences. 

Source: National Institute of Diabetes and Digestive and Kidney Diseases