Fecal Occult Blood Test

(FOBT; Stool Occult Blood Test)


A fecal occult blood test (FOBT) looks for blood in the stool, also known as feces.

Reasons for Test    TOP

The test is used to screen for colon and rectal cancers.

It may also used to find blood in the stool if you are having belly pain, diarrhea, vomiting, lack of hunger, or other symptoms.

Colon Cancer in the Rectal Wall

Rectal cancer
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Polyp in the Colon Wall

Colon polyp
Copyright © Nucleus Medical Media, Inc.

Possible Complications    TOP

There are no major problems linked to having this test.

What to Expect    TOP

Prior to Test

To improve the accuracy of the test, you may be asked to:

  • Avoid certain medicines and foods such as:
    • Nonsteroidal anti-inflammatory drugs (NSAIDs) for 7 days before testing. If you are taking them daily for health problems, talk to your doctor before you stop taking them.
    • Red meats, cantaloupe, uncooked vegetables, blood sausage, and hot sauce for 3 days before testing
  • Wait until your hemorrhoids are not bleeding.
  • Avoid having the test during your menstrual cycle.
  • Avoid cleaning your toilet bowl for a few days before the test. Cleansers 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 using the instructions. The kit should allow you to collect 3 samples. Some kits have a disposable container into which you can pass your bowel movement. Other kits give you tissue paper or plastic wrap that you can lay in the toilet to keep your stool from getting into the water.

You can also turn off the water valve to the toilet tank and flush the toilet a couple of times. This will 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 back on.

Using thin wooden sticks from 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    TOP

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

How Long Will It Take?    TOP

The test should only take a few minutes.

Will It Hurt?    TOP

This test will not hurt.

Results    TOP

If blood is found in your stool, you may need more tests. These tests will help to find out the cause of the bleeding. Although cancer may be one cause of blood in the stool, there are many other causes such as hemorrhoids, ulcers, or blood swallowed from a nosebleed.

Call Your Doctor    TOP

Call your doctor if you have:

  • Any new symptoms
  • Worsening of current symptoms

If you think you have an emergency, call for emergency medical services right away.


Family Doctor—American Academy of Family Physicians
National Institute on Aging


Canadian Digestive Health Foundation


Colorectal cancer screening. EBSCO DynaMed Plus website. Available at: http://www.dynamed.... Updated May 21, 2018. Accessed July 20, 2018.
Colorectal cancer screening tests. American Cancer Society website. Available at: https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/screening-tests-used.html. Updated May 30, 2018. Accessed July 20, 2018.
Fecal occult blood test and fecal immunochemical test. Lab Tests Online—American Association for Clinical Chemistry website. Available at: https://labtestsonline.org/tests/fecal-occult-blood-test-and-fecal-immunochemical-test. Updated July 13, 2018. Accessed July 20, 2018.
Last reviewed June 2018 by James Cornell, MD
Last Updated: 7/20/18

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