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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 (feces).

    Reasons for Test

    An FOBT is used mainly as part of the colorectal cancer screening process.
    It may also used to detect blood in your stool if you are having abdominal pain, diarrhea, vomiting, decreased appetite, or other symptoms.
    Colorectal Cancer
    Rectal cancer
    Copyright © Nucleus Medical Media, Inc.
    Adenomatous Polyp in Colon
    Colon polyp
    Copyright © Nucleus Medical Media, Inc.

    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 medicines or hemorrhoids or eating certain foods can cause a positive test. To help avoid this, you can try to:
      Avoid certain medicines and foods:
      • Nonsteroidal anti-inflammatory drugs, such as ibuprofen, naproxen, or aspirin for seven days prior to testing (If these are taken daily for medical conditions, consult your doctor before discontinuing.)
      • Red meats for three days before testing
      • Cantaloupe, uncooked vegetables, blood sausage, and possibly Tabasco sauce for three 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.
    You will set up the kit according to the instructions when you are ready to have a bowel movement. The kit should allow you to collect three 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.
    Using thin wooden sticks provided with the kit, you will pick up a very small sample of stool. You will then smear the sample onto a special card. 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
    In case of an emergency, call for medical help right away.


    American Academy of Family Physicians http://www.aafp.org

    Senior HealthNational Institutes of Health http://nihseniorhealth.gov


    Canadian Digestive Health Foundation http://www.cdhf.ca

    Health Canada http://www.hc-sc.gc.ca


    Can colorectal polyps and cancer be found early? Colorectal cancer screening. American Cancer Society website. Available at: http://www.cancer.org/docroot/CRI/content/CRI%5F2%5F4%5F3X%5FCan%5Fcolon%5Fand%5Frectum%5Fcancer%5Fbe%5Ffound%5Fearly.asp. Updated May 2009. Accessed July 24, 2009.

    Causes of occult and obscure gastrointestinal bleeding. American Academy of Family Physicians website. Available at: http://www.aafp.org/online/en/home.html. Accessed on February 7, 2003.

    Guide to diagnostic tests: fecal occult blood test. Harvard Medical School Health Publications website. Available at: https://www.health.harvard.edu/diagnostic-tests/fecal-occult-blood-test.htm. Accessed on July 24, 2009.

    Home stool testing kit a better screening tool. American Cancer Society website. Available at: http://www.cancer.org/docroot/home/index.asp. Published March 2001. Accessed on February 7, 2003.

    Pignone M, Campbell M, Carr C, et al. Proposed Effects of Dietary and Medication Restrictions during FOBT with guaiac-based tests. Meta-analysis of dietary restriction during fecal occult blood testing. Effective Clinical Practice. 2001;4:150-156.

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