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
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Adenomatous Polyp in Colon

Colon polyp
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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 occurs:

  • Development of any new symptoms
  • Worsening of existing symptoms
In case of emergency, call 911.