How Does Inflammatory Bowel Disease (IBD) Differ From Irritable Bowel Syndrome (IBS)?

How Does Inflammatory Bowel Disease (IBD) Differ From Irritable Bowel Syndrome (IBS)?

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are both conditions affecting the gastrointestinal (GI) tract. Although their names may be similar, they are two very different disorders.

Who Gets IBS vs. IBD?


About 12.0% of adults in the United States have IBS. It is not passed on through the genes, however it tends to occur more often within families. It affects more women than men. And, it is most common in those less than 50 years old.


About 1.3% of adults in the U.S. were diagnosed with IBD in 2015. It does seem to be passed on through genes, i.e. a family history of IBD increases the risk of developing it. It affects women and men equally. Although it is usually diagnosed when a person is in their teens to 30s, it is most common in those over 45 years old

What Is IBS?

Irritable bowel syndrome (IBS) is a functional bowel disorder. That means there is a problem with the normal function of the bowel - i.e. how it works. There may be a change in the muscle layer of the bowel, the way the nerves of the bowel work, or the way the brain controls the bowel.

The main symptoms of IBS, as you may know, are abdominal (belly) discomfort or pain and changes in bowel movements. Diarrhea, constipation, or a combination of both may occur.

Because there is a change in function, not structure, changes are usually not detected by diagnostic tests.

How Is IBD Different?

Inflammatory bowel disease (IBD) has two main types: ulcerative colitis (UC) and Crohn’s disease. UC affects the colon (large bowel) and rectum and Crohn’s disease can affect any part of the GI tract.

IBD is very different from IBS. Although there are symptoms that interfere with daily activities, it doesn’t have the more serious symptoms and possible outcomes of IBD. 

IBS and IBD do have some of the same symptoms, including chronic, recurring abdominal pain and diarrhea (as in IBS with diarrhea [IBS-D]). Bloating and gas may also occur with both IBS and IBD.

A person with IBD usually also has rectal pain or bleeding, bloody stool, and other GI symptoms. They may also have symptoms that affect the whole body, like tiredness, loss of appetite, weight loss, and fever. Symptoms may also affect other parts of the body, such as low iron levels (anemia), joint swelling, and problems with the eyes, skin, liver, and other organs.

With IBD, there are structural changes or damage to the bowel. They are seen with imaging and endoscopy, the use of a scope to view the GI tract. Because IBD is inflammatory, due to an immune system reaction, blood and stool tests are usually abnormal

Because of the damage to the bowel, people with IBD usually require long-term prescription medicines and close monitoring. Some also require hospital stays and surgery. There is also an increased risk of serious complications, including colorectal cancer. Thus, those with IBD should have regular colonoscopies.


  • IBS is most common in those less than 50 years old.

  • IBD is more common in those more than 45 years old.

  • IBS is a functional bowel disorder. Diagnostic tests aren’t usually done.

  • IBD causes structural GI tract changes. Diagnostic tests show inflammatory changes.

  • IBS symptoms include abdominal pain, diarrhea, constipation, or both.

  • IBD symptoms include abdominal pain, diarrhea, rectal bleeding or pain, stool with blood, tiredness, and weight loss.

For More Information

Centers for Disease Control and Prevention (CDC) (2022). What Is Inflammatory Bowel Disease (IBD)?. Retrieved 11-28-2022 from

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (2017). Irritable Bowel Syndrome. Retrieved 11-28-2022 from