Symptoms & Causes of Ulcerative Colitis

What are the symptoms of ulcerative colitis?

Symptoms of ulcerative colitis vary from person to person. Common symptoms of ulcerative colitis include

Symptoms of ulcerative colitis may vary in severity. For example, mild symptoms may include having fewer than four bowel movements a day and sometimes passing blood with stool. Severe symptoms may include having more than six bowel movements a day and passing blood with stool most of the time. In extremely severe—or fulminant—ulcerative colitis, you may have more than 10 bloody bowel movements in a day.3,4

Some symptoms are more likely to occur if ulcerative colitis is more severe or affects more of the large intestine. These symptoms include

You may have periods of remission—times when symptoms disappear—that can last for weeks or years. After a period of remission, you may have a relapse, or a return of symptoms.

Man with abdominal pain.
Common symptoms of ulcerative colitis include diarrhea, rectal bleeding, and pain in the abdomen.

What causes ulcerative colitis?

Doctors aren’t sure what causes ulcerative colitis. Experts think that the following factors may play a role in causing ulcerative colitis.


Ulcerative colitis sometimes runs in families. Research suggests that certain genes increase the chance that a person will develop ulcerative colitis.

Abnormal immune reactions

Abnormal reactions of the immune system may play a role in causing ulcerative colitis. Abnormal immune reactions lead to inflammation in the large intestine.


The microbes in your digestive tract—including bacteria, viruses, and fungi—that help with digestion are called the microbiome. Studies have found differences between the microbiomes of people who have IBD and those who don’t. Researchers are still studying the relationship between the microbiome and IBD.


Experts think a person’s environment—one’s surroundings and factors outside the body—may play a role in causing ulcerative colitis. Researchers are still studying how people’s environments interact with genes, the immune system, and the microbiome to affect the chance of developing ulcerative colitis.


Last Reviewed September 2020
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.