Irritable Bowel Syndrome: Symptoms, Diagnosis, & Treatment

By Edo Paz, MD
Medically reviewed checkmarkMedically reviewed
July 10, 2019

Irritable bowel syndrome or IBS may be the cause of your long-term stomach ache or abdominal pain. If you suffer from IBS, know that you are not alone. In fact, IBS is the most common functional gastrointestinal disorder and it affects more than 1 in 10 adults. This means there has been plenty of research and work carried out on IBS to help you manage this chronic condition. Read on to learn about the symptoms and causes of IBS, how you can find relief from IBS, and know when to see a doctor.

What Is Irritable Bowel Syndrome?

Irritable bowel syndrome affects the large intestine (or colon) and can cause a wide range of symptoms. Patients with IBS have a colon that is overly-sensitive to the natural contractions that move food through the intestines. Common symptoms include frequent abdominal pain, bloating, and gas. The pain you feel in your abdomen may change when you defecate, and changes in your bowel movements can cause diarrhea, constipation, or both.

Since IBS is a functional gastrointestinal (GI) disorder, it means that your gut is not functioning properly. While the exact causes are not known, IBS is associated with a variety of triggers, including stress, depression, anxiety, or a previous intestinal infection. Rest assured that having IBS does not mean that you suffer from physical damage such as ulcers, inflammation, or damage to your gut lining. IBS will also not cause abnormal results in a blood test.

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How Is IBS Diagnosed?

There’s no single test to definitively diagnose IBS. Rather, IBS is usually diagnosed after all other conditions are ruled out. If you think you might have IBS, your doctor will likely review your complete medical history, conduct a physical exam and run tests to check for other conditions with overlapping symptoms. If you have IBS and diarrhea, you may be tested for gluten intolerance or celiac disease.

After other conditions have been ruled out, your doctor is likely to use one of the following sets of diagnostic criteria for IBS:

The ROME Criteria

IBS is diagnosed when you have experienced abdominal pain and discomfort at least one day a week, each week during the last three months, and where at least two of the following factors are true:

  • Your pain and discomfort are related to when you pass stools.
  • The frequency of when you pass stools is altered.
  • The appearance of your stools is altered.

According to the latest updated ROME criteria, the clinical diagnosis of IBS can be divided into the following main subtypes:

  1. IBS with constipation (IBS-C)
  2. IBS with diarrhea (IBS-D)
  3. Mixed IBS where you have both constipation and diarrhea (IBS-M)
  4. Unsubtyped IBS

It is a good idea for you and your doctor to know which subtype of IBS you have because it will influence your treatment and dietary recommendations. Below are two charts which outline the various types of stool consistency and frequency. These guidelines can help you determine your IBS subtype.

The Manning Criteria

A different set of criteria is the Manning criteria, in which IBS is diagnosed when you have at least three of the following symptoms:

  • Your pain started with more frequent bowel movements.
  • Your pain started with looser stools.
  • Your pain is relieved when you pass stools.
  • You have noticeable abdominal bloating.
  • You feel like you’re not completely evacuating your stools more than 1 in 4 times you go to the bathroom.
  • You have diarrhea with mucus more than 1 in 4 times you go to the bathroom.

IBS Symptoms to Watch For

Your doctor will also check for other signs or symptoms, which could be a sign of a more serious condition.

If you have any of these symptoms, your doctor will likely run additional tests to rule out other conditions.

Common Tests Used to Rule Out or Diagnose IBS

When a doctor suspects you might have IBS, they will run a variety of tests to try and identify the cause of your discomfort and to check for other conditions that have similar symptoms.

Common tests include:

Imaging tests:

  • Colonoscopy – The entire length of your colon is examined with a flexible tube.
  • Flexible sigmoidoscopy – The lower part of your colon is examined with a flexible, lighted tube called a sigmoidoscope.
  • X-ray or CT scan – Both these tests capture images of the inside of your abdomen and pelvis. You may need to drink a barium liquid to help reveal problem areas in the scan.

Laboratory tests:

  • Lactose intolerance tests – People who can’t produce lactase, the enzyme needed to digest the sugar found in dairy products, may experience symptoms similar to those of IBS. For that reason, doctors will look to rule this out when diagnosing IBS.
  • Breath test for bacterial overgrowth – This test detects bacterial overgrowth in your small intestine. It is more likely to happen in people with diabetes or another disease that slows down digestion. It can also occur in patients who have had bowel surgery.
  • Upper endoscopy – This test can rule out celiac disease. Your doctor will insert a long, flexible tube with a camera on the end down your throat to look at your upper digestive tract. A small tissue sample (biopsy) and fluid is taken from your small intestine to check for any bacterial overgrowth.
  • Stool studies – This test checks your stool for the presence of bacteria or parasites, or for traces of the digestive liquid produced in your liver (bile acid).

Common Causes of IBS

The reasons why IBS develops are not clear. The latest ROME Criteria now emphasize how functional GI disorders, such as IBS, are disorders stemming from the interaction between your brain and your gut. That means that your intestines are connected to the brain via hormone and nerve signals that go back and forth between the bowel and the brain. These signals affect bowel function and symptoms. For example, the nerves can become more active during stress. This can cause oversensitivity in the intestines and more frequent contractions.

Your GI symptoms may be due to any combination of the following:

  • The movement of food and waste through the GI tract (“motility disturbance”)
  • Heightened experience of pain in the internal organs (“visceral hypersensitivity”)
  • Changes in the gut’s immune defenses (“altered mucosal and immune function”)
  • Changes in the community of bacteria in the gut (“altered gut microbiota”)
  • Changes in how the brain sends and receives from the gut (“altered central nervous system processing”)

In other words, changes in many different body processes can lead to IBS.

IBS can occur after a bacterial or parasitic infection of the intestines. This is called “post-infectious IBS.” What’s more, your overall health depends on the microflora, or “good” bacteria living in your intestines, and people with IBS may have an imbalance of these normal microflora. Every person has a unique composition of different types of bowel bacteria, which begin forming in childhood. The foods we eat can cause different types and amounts of bowel bacteria to multiply. These fluctuations in bacteria may cause the nerve cells or neurons controlling how your GI tract functions to signal abnormally, thus leading to your IBS symptoms. (Part of the “altered mucosal and immune function” and “altered gut microbiota” of the Rome Criteria listed above).

IBS can occur at any age, but onset is less likely in people over 50. Symptoms usually begin in the teen years, or in early adulthood. IBS is twice as common in women as in men.

Inflammatory Bowel Disease

Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis are often initially misdiagnosed as IBS. If you have an inflammatory bowel disease (IBD), your symptoms may include inflammation, bloating, gas, pain, and rectal bleeding.

The reasons for misdiagnosis are simple: IBS symptoms often overlap with IBD symptoms, IBS can occur together with IBD, and IBS is a much less serious diagnosis. If you don’t have a history of severe gastrointestinal disease, your doctor is more likely to diagnose you with IBS.

Unfortunately, the differences between IBS and IBD can often be difficult for doctors to spot. Unlike IBS, IBD is clinically diagnosable through a variety of blood tests, biopsies, and imaging tests. They are characterized by inflammation and physical damage that is visible in the gastrointestinal tract. What’s more, IBDs generally improve with medications targeted at the gut, whereas such medications do not always help with IBS.

Functional Dyspepsia

Functional dyspepsia is another gastrointestinal disease that has many symptoms in common with IBS. Functional dyspepsia involves the upper part of the GI tract and those who suffer from it experience stomach pain, nausea, bloating, and gas. Although functional dyspepsia is different than IBS, the physiological malfunctioning of the gut is similar in the two conditions. Researchers now think that these two common digestive system diseases should not be artificially split but be considered in combination as an ‘irritated gut’ and be treated together accordingly.

Gluten Sensitivity

Gluten sensitivity is where people experience indigestion, pain, bloating, and gas after consuming foods rich in gluten, such as bread and most starchy vegetables. These overlapping symptoms with IBS mean that it is often misdiagnosed.

Anxiety and Stomach Pain

There is a very strong connection between your brain and your gut. In fact, there may be more neurons in the human gut than the entire spinal cord.

IBS is considered a “stress-sensitive disorder.” This means that many people who have IBS also suffer from depression or anxiety. Anxiety may increase your stomach ache or stomach pain. This is especially true if you have the IBS-C (predominantly constipation) subtype. A possible explanation for this is due to the actions of 5-hydroxytryptamine (5-HT), otherwise known as serotonin, which influences your feelings of happiness.

Serotonin is an important chemical and neurotransmitter which is essential in maintaining GI motility, visceral sensitivity, GI immune function, and blood flow.

If you have the IBS subtype IBS-D (predominant diarrhea), then you are more likely to have increased serotonin production which leads to rapid GI motility and increased blood flow, and so contributes to IBS-related diarrhea. Whereas, if you have the IBS-C subtype, you have a greater concentration of serotonin in the innermost membrane of your colon which means that serotonin is not released sufficiently. This is why sufferers with IBS-C report feeling less happy, and often experience more stress and anxiety.

IBS Treatment

Although IBS may be frustrating to deal with, it fortunately does not increase your risk of colon cancer or other serious bowel problems. There is no cure for IBS, but with an accurate diagnosis, and an understanding of the foods and situations (such as stress) that trigger your symptoms, you can lead a healthier life that is not controlled by your IBS.

Since it is now understood that IBS results from an interaction between your brain and your gut, doctors can help you manage your condition by providing a more interdisciplinary approach. Keep in mind that IBS is not solely a physical condition. In most cases, both psychological and social factors contribute to the onset of IBS. This means that your doctor may treat you by considering many factors such as:

  • Early life influences: genetics, culture, environment.
  • Psychosocial factors: your personality, stress level, mental and emotional well-being, how you are generally able to cope and what social support you have
  • Physiological factors: motility, sensation, immune function, microflora, food, and diet

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What to Eat If You Have IBS (And What Not to Eat)

Making changes to your diet can help you reduce and control your IBS symptoms. It is important to remember that foods do not cause a person to develop IBS, and neither does the digestive process itself. Rather, the symptoms of IBS are due to the muscles and nerves in your gut over-reacting due to hormones that are released when you digest food.

Certain food triggers can cause IBS symptoms to worsen. You may have a variety of food triggers, and these can change over time. Different people with IBS may have different food triggers so identifying and avoiding your own personal IBS food triggers will greatly help you manage your IBS. It may be difficult to differentiate between a food allergy or intolerance, and an actual IBS trigger. This process will therefore usually require a great deal of trial and error.

Tracking What You Eat to Identify Food Triggers

An effective strategy to identify your own personal food triggers is to keep a diary for 2-3 weeks of what you eat, along with which symptoms you have and when you have them. Your doctor can then review the diary with you and help you to pinpoint potential food triggers. This will help you and your doctor to develop a balanced and nutritious diet that avoids those triggers.

General Tips for Managing IBS Symptoms

If you have IBS, avoid eating large meals. Instead, try to eat smaller meals more frequently.

It helps to look into your fiber intake as depending on the type of IBS too much or too little fiber can cause problems:

  • Diarrhea suffers can try reducing insoluble fiber. Some examples are: whole grain wheat, nuts, bran and cereals.
  • Constipation suffers can try increasing their soluble fiber intake. Examples are: oats, banana, apple, barley.

Some common foods that can trigger IBS symptoms of cram`ping and diarrhea include:

  • Alcohol
  • Chocolate
  • Caffeinated drinks, such as coffee, tea, or soda
  • Dairy products, such as milk and cheese
  • Augar-free (artificial) sweeteners, such as mannitol, sorbitol, Xylitol, and maltitol
  • Chocolate
  • Nuts
  • Insoluble fiber, such as cereal
  • Foods containing fructose, such as honey and some types of fruits
  • Fried foods
  • Meals high in fat

People with gas that is caused by IBS may find that triggers include foods like:

  • Beans
  • Cabbage
  • Cauliflower
  • Broccoli
  • Legumes, such as peas, peanuts, and soybeans
  • Brussel sprouts
  • Raisins
  • Onions
  • Bagels
  • Insoluble fiber, such as cereal

What Diets Reduce IBS Symptoms?


Your doctor may recommend that you try a special diet called “low FODMAP.” FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. Saccharide is simply another word for sugar. Basically, FODMAPs are carbohydrates that are readily fermented by bacteria.

When following the low FODMAP diet, you will avoid foods that can be hard to digest; which may help you to control your IBS symptoms. It is important you consult with your doctor before going on the low FODMAP diet to make sure that you are still getting all the nutrients you need in your diet.

As part of this dietary strategy, your doctor may recommend you to avoid or eliminate foods that are known as “high FODMAP.” These include:

  • Dairy products
  • Foods that contain wheat or rye
  • Foods that contain high-fructose corn syrup or honey
  • Artificial sweeteners
  • Certain vegetables, including mushrooms, onions, artichokes, beans, cabbage, asparagus, snow peas, cauliflower, garlic, and lentils
  • Some fruits and fruit juices, including watermelon, pears, apples, plums, apricots, blackberries, mango, cherries, and nectarines

The BRAT Diet

The BRAT diet is sometimes used for the treatment of diarrhea. That is, a diet of Bananas, Rice, Applesauce, and Toast. Since the foods included in the BRAT diet are low in protein, fat, and fiber, they are considered to be easily digestible. However, this diet is very restrictive and shouldn’t be used long-term since you will not be ingesting enough nutrients and calories. For this reason, many doctors no longer recommend BRAT as a treatment option.

IBS Prevention and Tips for What You Can Do at Home


As we have discussed, diet is very important and it always helps to ensure you eat properly and regularly, and avoid missed meals or long gaps between eating. Try and cut back on high FODMAP foods (listed above) and anything you have noticed or recorded in your food diary that can trigger your symptoms.

If you would like to try probiotics to improve your gut’s microflora, make sure you take the product for at least 4 weeks and record any changes in your symptoms and general well-being. Probiotics should be taken at the dose recommended by the manufacturer.


Exercise can help reduce symptoms of IBS and can help your body combat the symptoms. It may be helpful to do 30 minutes of exercise daily, or one hour every couple of days. Talk to your doctor to advise you on which exercises are suitable for you.

Reducing Stress

Reducing stress can have a significant impact on ameliorating symptoms of IBS. It can help reduce both the frequency and severity of your symptoms, particularly because stress can be a main cause of IBS. Physical exercise and relaxation techniques such as breathing exercises, yoga, and meditation can all help. You may want to take a step back and see what could be causing you stress in your life, and to think about how to minimize it. Some IBS sufferers have found relief after seeing stress counsellor or cognitive behavioral therapist. Hypnotherapy is another possible avenue for reducing generalized stress and anxiety.

IBS Medication

Many people can keep their IBS under control by managing their diet, lifestyle, and stress levels. Medication can help reduce symptoms, but they cannot cure IBS. You can try over-the-counter painkillers and fiber pills, or consider alternative treatments, such as peppermint oil.

Talk to your doctor if you feel you want to try treating your symptoms with medication. These medications target different symptoms:

  • Antispasmodic medicines – help reduce cramping and abdominal pain
  • Antimobility medicines – treat symptoms of diarrhea
  • Laxatives – for symptoms of constipation
  • Antidepressants – in small doses, these medicines are known to reduce pain and mobility of the gut

Find a doctor you are comfortable talking to about your symptoms, even if the symptoms seem embarrassing. Your goal of treatment is to allow you to function normally in your daily activities and lessen the discomfort. Usually, treatment involves a combination of strategies, and you may need to see the doctor several times to find the best management plan for your symptoms. Even after you have found a treatment combination that works for you, it is still a good idea to continue seeing your doctor to monitor your condition.

When to Seek Help for IBS

See your doctor if you have a persistent change in bowel habits or other signs or symptoms of IBS. They may indicate a more serious condition, such as colon cancer. More-serious signs and symptoms include:

  • Weight loss
  • Diarrhea at night
  • Rectal bleeding
  • Iron deficiency anemia
  • Unexplained vomiting
  • Difficulty swallowing
  • Persistent pain that isn’t relieved by passing gas or a bowel movement

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Edo Paz, MD

Edo Paz is the VP of Medical at K Health. Dr. Paz has two degrees in chemistry from Harvard and earned his medical degree from Columbia University. He did his medical training in internal medicine and cardiology at New York-Presbyterian. In addition to his work at K Health, Dr. Paz is a cardiologist at White Plains Hospital, part of the Montefiore Health System.