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Fecal Occult Blood Test

(FOBT; Stool Occult Blood Test)


A fecal occult blood test (FOBT) is a test to detect the presence of blood in the stool, also known as feces.

Reasons for Test

An FOBT is used to screen for colon and rectal cancers.
It may also used to detect blood in the stool if you are having abdominal pain, diarrhea, vomiting, decreased appetite, or other symptoms.
Colon Cancer in the Rectal Wall
Rectal cancer
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Polyp in the Colon Wall
Colon polyp
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Possible Complications

There are no major complications associated with this test.

What to Expect

Prior to Test

A positive FOBT does not mean you have cancer. Other things can cause a positive test. Minor stomach bleeding from certain medications, hemorrhoids, or eating certain foods can cause a positive test. To help avoid this:
  • Avoid certain medications and foods, such as:
    • Nonsteroidal anti-inflammatory drugs (NSAIDs) for 7 days prior to testing. If you are taking them daily for medical conditions, talk to your doctor before you stop taking them.
    • Red meats, cantaloupe, uncooked vegetables, blood sausage, and possibly hot sauce for 3 days before testing
  • Wait until your hemorrhoids are not bleeding.
  • Avoid having the test during your menstrual period.
  • Avoid cleaning your toilet bowl for several days before the test. Chemicals from the cleanser can affect the test.

Description of Test

The test is most often done at home.
When you are ready to have a bowel movement, you will set up the kit according to the instructions. The kit should allow you to collect 3 samples of stool. Some kits provide a disposable container into which you can pass your bowel movement. Other kits provide you with tissue paper or plastic wrap that you can lay in the toilet to keep your stool sample from sinking into the water.
Another option is to turn off the water valve to the toilet tank and flush the toilet a couple of times to empty most of the water out of the toilet bowl. When ready, pass the bowel movement into the bowl. Collect the sample, then turn the water supply back on to allow for flushing.
Using thin wooden sticks provided with the kit, you will pick up a small sample of stool. You will then smear the sample onto a special card. If you do not have hemorrhoids, some doctors may allow you to smear the sample onto the card with stool from toilet paper. The card folds over to protect the stool sample.

After Test

You will mail or deliver the cards to the clinic or lab. Make sure you have written your name on each card.

How Long Will It Take?

The test should only take a few minutes.

Will It Hurt?

This test will not hurt.


If blood is found in your stool, you may be asked to have additional tests. These tests will help to determine the cause of the bleeding. Although cancer may be one cause of blood in the stool, there are many other causes.

Call Your Doctor

After the test, call your doctor if any of the following occur:
  • Development of any new symptoms
  • Worsening of existing symptoms
If you think you have an emergency, call for emergency medical services right away.


Family Doctor—American Academy of Family Physicians
Senior Health—National Institutes of Health


Canadian Digestive Health Foundation
Health Canada


Can colorectal polyps and cancer be found early? Colorectal cancer screening. American Cancer Society website. Available at: Updated January 20, 2016. Accessed March 9, 2016.
Pignone M, Campbell M, Carr C, Phillips C. Meta-analysis of dietary restriction during fecal occult blood testing.. Eff Clin Prac. 2001;4(4):150-156.

Revision Information

  • Reviewer: EBSCO Medical Review BoardJames Cornell, MD
  • Review Date: 03/2017
  • Update Date: 03/09/2016
Article written by Scholten A