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Fecal Occult Blood Test

  • Cynthia M. Johnson, MA
Publication Type:


Fecal Occult Blood Test

(FOBT; Stool Occult Blood Test)


A fecal occult blood test (FOBT) looks for blood in the stool.

Reasons for Test

The test is done to screen for colon and rectal cancers. It may also be done to look for causes of belly pain, diarrhea, vomiting, or lack of hunger.

Colon Cancer in the Rectal Wall

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Possible Complications

There are no major problems linked to having this test.

What to Expect

Prior to Test

Your care team may meet with you to talk about:

  • Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the test
  • Avoiding certain foods in the days leading up to the test
  • Not having the test during a menstrual cycle
  • Waiting until any hemorrhoids that you may have are no longer bleeding
  • Not using toilet bowl cleaners in the days before taking the test

Description of Test

This test is often done at home using a kit. The kit will have instructions.

Use the instructions to set up the kit when you are ready to have a bowel movement. The kit should let you collect 3 samples. Some kits have a disposable container that can be used to pass the bowel movement into. Other kits have tissue paper or plastic wrap that can be put in the toilet to keep the 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. Pass the stool into the bowl when you are ready. Collect the sample and turn the water back on.

Pick up a sample of small stool using the thin wooden sticks in the kit. Smear the stool onto the card. Fold the card over to protect the stool sample.

After Test

The card may need to be mailed or brought into a clinic. Make sure your name is 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 need more tests. These tests can help find the cause of the bleeding.

Problems To Look Out For

Call your doctor if you have new or worsening symptoms.

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





  • Cobo-Cuenca, A.I., Laredo-Aguilera, J.A., et al. Temporal trends in fecal occult blood test: associated factors (2009-2017). International Journal of Environmental Research and Public Health, 2019; 16 (12): 2120.
  • Colorectal cancer screening. EBSCO DynaMed website. Available at:
  • Colorectal cancer screening tests. American Cancer Society website. Available at:
  • Fecal occult blood tests. Cancer.Net website. Available at:
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.