Irritable bowel syndrome (IBS) is a gut disorder that may cause cramps, bloating, and bouts of constipation and diarrhea, among other symptoms.

Disrupted communication between the gut and brain causes the signs and symptoms of irritable bowel syndrome (IBS).

Historically, people thought IBS to be a functional gastrointestinal disorder, which means it is caused by abnormal functioning and not a tumor or infection. However, researchers have found that small intestinal bacterial overgrowth may play a role in the condition for some people.

Research is still ongoing into exactly why some people get IBS. It may be that their gut is especially sensitive to stress or certain foods.

Around 12 percent of adults in the United States have IBS. Women are twice as likely to have IBS as men. It is also more common in people under the age of 50 years.

In this article, we explore 10 symptoms of IBS. Read on to learn how to recognize it. We also discuss other conditions that could cause similar symptoms.

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Pain and cramping in the lower abdomen can be symptoms of conditions ranging from minor to serious. They are two of the main symptoms of IBS.

An oversensitivity of the gut likely causes these symptoms.

IBS affects how the brain and gut work together, and the condition may cause the muscles in the gut to contract more than they need to for a normal bowel movement. Excessive contraction of the gut muscle may lead to lower abdominal pain and cramping.

A 2014 review found that IBS was the third most common diagnosis made by general practitioners for pain and cramping in the lower abdomen after “no diagnosis” and gastroenteritis. Less commonly, the pain is caused by:

  • urological issues
  • gastritis
  • appendicitis
  • diverticulitis
  • pancreatic disease
  • endometriosis
  • pelvic inflammatory disease
  • inflammatory bowel disease
  • ovarian cancer

Emergency room doctors may use ultrasounds and blood tests to rule out other conditions.

They may also ask a person questions about:

  • their medical history
  • pain patterns, such as any link to the menstrual cycle
  • other symptoms, such as bloating, constipation, or diarrhea
  • possible food triggers
  • recent travel

If there are no other factors involved, they may make a diagnosis of IBS.

People with IBS may experience excessive gas. Doctors do not know the exact reason for this, though there are several theories.

One theory is that IBS causes a problem with bacteria in the gut. Bacteria can create certain toxins that may cause excessive gas.

Another theory is that people with IBS are less able to tolerate and transport gas in their gut, which leads to a feeling of gassiness.

Gas often accompanies other symptoms, such as bloating, constipation, and belching. If the onset occurs half an hour after eating, it could be due to IBS. Doctors may screen for celiac disease in this case.

Symptoms indicating something more serious include:

  • a lump in the abdomen
  • difficulty or pain when swallowing
  • intense diarrhea
  • fever
  • gastrointestinal bleeding
  • jaundice
  • constipation
  • new symptoms in someone 55 years or older
  • family history of colon cancer or pancreatitis

Doctors may ask a person about their family medical history and eating and drinking habits to understand possible causes. A rectal examination can determine if there is pelvic floor dysfunction.

Feeling bloated is another symptom of IBS. Bloating refers to a collection of gas in the gut, which can cause the abdomen to feel full and appear rounder than usual. A person may also feel bloated without their belly being rounded.

The same factors that cause excessive gas in IBS may also cause bloating.

Other causes of bloating include:

  • celiac disease
  • small intestinal bacterial overgrowth
  • specific foods, such as beans and legumes

Bloating that occurs with constipation will be evaluated for signs of other conditions, including:

  • pelvic floor dysfunction
  • chronic constipation
  • slow-transit constipation

Observing any pattern related to bloating and meal consumption can provide clues as to whether IBS may be to blame.

Diarrhea is a key symptom of IBS. It happens because the muscles in the gut contract more than they need to. A feeling of muscle cramps may accompany diarrhea.

To produce a bowel movement, the gut contracts and relaxes in a rhythmic way. In IBS, however, this rhythm is disrupted. IBS can either speed up or slow down gut muscle contractions, meaning it can cause both constipation and diarrhea at different times.

IBS that occurs mostly with diarrhea is called IBS-D. It appears in about a third of people with IBS. It is more common in men.

As with other IBS symptoms, diarrhea can be related to how the brain and gut communicate. Research into exactly why this happens is ongoing.

Symptoms indicating something more serious include:

  • diarrhea lasting more than two weeks
  • unintended or sudden weight loss
  • blood in the stool
  • fever

A doctor will want to know if there is a family history of colon cancer, celiac disease, or inflammatory bowel disease.

Doctors may use a hydrogen breath test to rule out lactose intolerance and small intestinal bacterial overgrowth.

Constipation occurs when a person finds it difficult to pass stool. A person has constipation when they have:

  • fewer than three bowel movements in a week
  • hard, dry, or lumpy stools
  • difficulty or pain when passing stool
  • a feeling of an incomplete bowel movement

There are many possible causes of constipation, including dehydration, a lack of fiber in the diet, and stress. IBS can also cause constipation by affecting how the muscles in the gut contract.

When someone is constipated, their gut muscles do not contract as much as they should.

IBS that occurs mostly with constipation, and with only occasional diarrhea, is called IBS-C. It can be hard to distinguish from chronic idiopathic constipation, which is another functional gastrointestinal disorder.

Constipation is a common ailment. If it cannot be relieved with treatment, or if additional signs emerge, doctors may want to rule out more serious conditions. These include:

  • colorectal cancers
  • hypothyroidism
  • pelvic floor dysfunction

People with IBS may be more sensitive to foods high in FODMAPs, which are “fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.” These are types of carbohydrates that can cause inflammation or irritation in the gut.

FODMAPs can increase the amount of water going into the gut, and bacteria in the gut may cause them to ferment. This can increase intestinal gas.

People may be able to reduce the symptoms of IBS by avoiding high FODMAP foods, which include:

  • onions
  • avocados
  • lentils
  • garlic
  • beans
  • almonds
  • cashews

For many people with IBS, eating FODMAPs triggers other signs and symptoms of the condition. A 2017 meta-analysis found that consuming a low FODMAP diet may relieve symptoms of IBS.

A 2018 meta-analysis found weaker support for the impact of a low FODMAP diet.

As many as half of people with IBS experience fatigue or exhaustion.

A 2016 review found that fatigue occurred alongside other IBS symptoms, including bowel-related symptoms, psychological distress, and health-related impacts on quality of life. It was also found to be more common among younger females.

A 2018 study found a possible link between dysfunctional regulation of serotonin and fatigue in women with IBS. More research is needed into possible genetic markers for a predisposition to fatigue.

Medical professionals still do not fully understand why IBS sometimes leads to fatigue.

People with IBS may be more likely to experience joint pain. Scientists still do not know why, but it may be due to increased inflammation in the body.

A 2019 study found that eating a low FODMAP diet relieved symptoms of joint hypermobility syndrome for people with IBS. The results were strongest for people with IBS-C.

A 2017 study found that people with IBS had an increased risk of a type of joint pain called temporomandibular disorder. However, more research is needed to understand this link.

There is a strong link between IBS and stress. As many as three-quarters of people with IBS report stress. The nervous system controls the gut and also responds to psychological stress.

The link between IBS and stress goes both ways. Feeling stressed can worsen IBS symptoms, and the physical symptoms of IBS can cause psychological distress.

A 2021 study found that chronic stress and a lack of sleep were associated with self-reported IBS. Stress in the shorter term was strongly associated with reports of gastrointestinal symptoms.

Intestinal gas and bloating, which are symptoms of IBS, are also linked with brain fog.

Brain fog, or foggy thinking, describes mental confusion, impaired judgment, and trouble concentrating.

More research is needed to fully understand the link between problems with the gut and brain fog.

IBS can be stressful for those experiencing symptoms. People who experience discomfort or pain should talk with their doctor.

Doctors use the Rome IV criteria for evaluating possible cases of IBS. To qualify, a person will have:

  • abdominal pain that occurs at least once a week for three months
  • abdominal pain that occurs in a pattern with bowel movements
  • changes in the frequency or consistency of stool

Doctors will conduct tests to rule out other conditions. They may conduct:

  • an abdominal exam
  • a rectal exam
  • blood tests
  • breath tests

Concerning symptoms include:

  • unintentional weight loss
  • pain at night
  • blood in stool
  • fever
  • family history of colorectal cancer

IBS is not the only explanation for the symptoms explored in this article. It is best to speak to a doctor to get an accurate diagnosis.

Experiencing excessive gas or bloating does not necessarily mean that a person has IBS. If they start to become gassy soon after eating, they may have small intestinal bacterial overgrowth.

Also, getting diarrhea frequently or urgently may be a sign of:

Constipation may be a condition in itself. It could also indicate:

  • a problem with the pelvic floor muscles
  • disease in the colon
  • disease in the rectum

Doctors will look for patterns in IBS symptoms and factors such as:

  • symptom onset around meals
  • types of foods eaten
  • other symptoms that occur at the same time
  • family and medical history of other conditions

Here are some frequently asked questions about IBS.

What foods trigger IBS?

Food triggers for IBS may be different for each person. Some research suggests that a low FODMAP diet can help ease symptoms, which suggests that people with IBS may benefit from avoiding high FODMAP foods. Examples include onions, lentils, garlic, avocado, and beans.

Keeping a food diary can help a person identify foods that may trigger or worsen their IBS symptoms.

Learn more about foods to avoid with IBS.

How do you know if you have IBS?

IBS can cause symptoms such as abdominal pain and changes in bowel habits. A person may have either diarrhea or constipation, or both. It can also cause bloating and mucus in stool.

It is best for a person to contact a doctor if they experience a fever or black or bloody stool. A doctor can review a person’s symptoms and medical history to assist with diagnosing IBS.

What exactly does IBS feel like?

IBS can cause abdominal pain or cramps, bloating, and a feeling like the bowel movement is incomplete. It can also cause back pain and feelings of tiredness and nausea.

IBS is a long-term health condition that can affect a person’s well-being if they do not seek treatment. Understanding the signs and symptoms of IBS can help a person experiencing it get appropriate help.

Many treatment options are available to help a person with IBS manage their condition. Many of these focus on the link between stress and IBS. A doctor may also recommend counseling and progressive relaxation techniques as a way to ease symptoms.