Ulcerative Colitis Diagnosis, Testing, and Treatments

Medically Reviewed By Cynthia Taylor Chavoustie, MPAS, PA-C
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Testing for ulcerative colitis may involve blood and stool tests and a procedure called an ‘‘endoscopy.’’ Ulcerative colitis is an autoimmune disease that causes inflammation and sores in the inner lining of the large intestine. Ulcerative colitis can be difficult to diagnose because its symptoms are similar to other intestinal problems, including Crohn’s disease. 

Keep reading to learn more about the diagnostic process for ulcerative colitis, including what tests to expect.

Initial testing and evaluation

A woman with her hands on her stomach
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The first step in reaching a diagnosis is seeing a gastroenterologist, a doctor specializing in intestinal problems. Some people refer to gastroenterologists as GI (gastrointestinal) doctors. 

The doctor will ask you about your:

  • medical history
  • general health
  • family history
  • home environment
  • daily activities
  • diet

Partner with your doctor to identify the problem. With a correct diagnosis, you can begin treatment and feel better.  

Understanding your symptoms

It’s important to provide as much information as possible about your symptoms and when they occur. This helps your doctor understand you and your condition. If possible, keep a journal of your symptoms and take it to your appointment. Log your bowel movements, bleeding, diarrhea, fevers, joint aches, and other symptoms. Write down when they start, how long they occur, and what makes them better or worse.

For example, you may log that you began an episode of diarrhea at 6:30 p.m., 30 minutes after eating a large meal, and noticed blood in the diarrhea. This kind of detail can help your doctor investigate your condition. 

Why an accurate diagnosis is important

If you have ulcerative colitis, your symptoms may be very similar to or even the same as someone with Crohn’s disease. Both are considered forms of inflammatory bowel disease. However, it’s important to know the exact cause and location of your inflammation. While some medications are used to treat ulcerative colitis and Crohn’s disease, some are targeted for treating only ulcerative colitis.  

According to a 2017 paper, assessing bloody stool and frequency, body temperature, and heart rate are all good indicators of the severity and outcome of ulcerative colitis.

To help your doctor make an accurate diagnosis, be patient and remain an active participant in your testing and care. Together, you can pinpoint the reason for your symptoms and get the therapy you need.

What to expect at your doctor’s visit

Once a doctor has asked about your medical and family history and symptoms, they may conduct a physical exam. This can involve:

  • checking your blood pressure, heart rate, and temperature, which can provide information about the severity of the condition
  • listening to your abdomen with a stethoscope
  • lightly pushing on your abdomen and feeling for tenderness or masses

A doctor may also recommend a digital rectal exam. This can check for blood in your stool.

Ulcerative colitis tests

A doctor will likely recommend blood and stool tests and an endoscopy for an accurate diagnosis of ulcerative colitis.

Blood tests

Researchers in a 2017 paper write that everyone should have a complete blood count during the initial stages of ulcerative colitis diagnosis.

A blood test can help identify a high white blood cell count, a signal of inflammation in the body. Blood tests can also detect if you are anemic, which can occur due to bleeding in the colon or rectum. 

Stool tests

A stool test involves collecting a stool sample and sending it for analysis. In addition to identifying high white blood cell counts, it can also help doctors rule out other causes of diarrhea, such as bacterial or viral infection

Although blood and stool tests are helpful, they may not always tell your doctor what is causing your intestinal problems. However, they confirm that more tests are needed to find the cause of the inflammation. 

Stool tests can also be useful if treatment is not working or a person’s ulcerative colitis has relapsed.


The standard tests doctors use to accurately diagnose ulcerative colitis is a colonoscopy or flexible sigmoidoscopy.


With a colonoscopy, your doctor can look inside the rectum and the entire colon using an endoscope. Your doctor may also take a painless small tissue sample or biopsy during the procedure.

A doctor analyzes the tissue to make the diagnosis. 

Flexible sigmoidoscopy

Sometimes your doctor may recommend a flexible sigmoidoscopy to diagnose ulcerative colitis. The test is similar to a colonoscopy but allows the doctor to view the rectum and only the lower colon. 

Surgeons remove small pieces of colon tissue to examine under a microscope. This should not be painful

A colon biopsy can also help doctors rule out colon cancer during ulcerative colitis diagnosis.


A chromoendoscopy can help doctors look for precancerous changes or polyps. Clinicians spray a blue liquid dye into the colon. This makes any changes to the lining of the intestine stand out more clearly.

They may then remove any polyps and send them for testing.

Many people find they have blue stools after this test.


The diagnosis procedure for ulcerative colitis usually involves a gastroenterologist asking you about your history and symptoms. They will then complete a physical exam and likely order some tests. Tests can include blood tests, stool tests, and varying types of endoscopy.

These tests are usually painless. Work closely with your doctor, and take diaries of your symptoms to all appointments to note any new symptoms or changes.

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Medical Reviewer: Cynthia Taylor Chavoustie, MPAS, PA-C
Last Review Date: 2022 Oct 29
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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