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There are currently three fecal tests that help determine whether colorectal cancer is present by looking for hidden (occult) blood in the stool. To learn about each test, click on the following link. .

Blood in the stool may be the only symptom of colorectal cancer, but not all blood in the stool is caused by cancer. If blood is present, additional tests such as a colonoscopy or sigmoidoscopy are needed to determine definitively if cancer is present.


FOBT (Fecal Occult Blood Test)

A fecal occult blood test can be given at home or it may be given in a doctor's office.  

A FOBT is usually given once a year.

Types of FOBTs

There are two types of FOBTs. Both start with taking tiny samples from three consecutive bowel movements which are put on a special card or cloth.

  • With a traditional guaiac smear test, the samples are sent to a lab where chemicals are added so any blood can be seen that cannot be seen just by looking at a sample. Doctors and other health care providers generally prefer the guiac smear because of its sensititivy and because large studies have shown the benefits of guaiac tests.
  • A newer test which involves flushable reagent pads. Many consumers prefer the flushable reagent pads because there is no stool handling and no laboratory processing. 

NOTE: It is important to follow the instructions that come with the test kit to ensure that the results are accurate. FOBT test kits are not expensive.

How to Prepare For An FOBT

To prepare for an FOBT, you will be instructed to avoid certain foods, supplements and medications for several days before you collect stool samples.

  • Some can cause false positives on the FOBT. A false positive means that the test will show you have colon cancer even if you don't. 
  • Some may create the opposite problem: they can cause a false negative.  A false negative means the test will show you do not have colon cancer, when in fact you do.
  • Some medications such as aspirin or ibuprofen can cause bleeding in your stomach or intestines.

Advantages of a fecal occult blood test:

  • No cleansing of the colon is necessary.

  • Samples can be collected in the comfort of your home.

  • The test can be simple to complete.

  • The cost is low compared with other colorectal cancer screening tests. Cost is covered by most health insurance.

  • FOBT does not cause bleeding or tearing/perforation of the lining of the colon.

Concerns related to using the fecal occult blood test include:

  • A fecal occult blood test does not detect polyps or lesions before they are cancerous. The test only detects blood in the stool.

  • The fecal occult blood test may miss some abnormalities. For example, the test may miss tumors that bleed in small amounts or not at all.

  • Patients may find the test unpleasant.

  • ????The dietary restrictions and changes, such as avoiding meat, certain vegetables, vitamin C, iron supplements and aspirin, and increasing fiber consumption. These restrictions and changes are often recommended for several days before a guaiac FOBT. These restrictions and changes are not required for FIT

  • Multiple days of stool collection.

  • Additional procedures, such as colonoscopy, may be needed if the test indicates an abnormality.

  • High false positive rates in which the test suggests an abnormality when there isn't one. Non-cancerous conditions may also cause blood in the stool.

  • The test must be done yearly to be considered a fairly reliable alternative to colonoscopy.

Fecal Immunochemical Test (FIT)

Fecal Innumochemical Test (FIT) involves submitting a small amount of a single bowel movement to your doctor's office for testing.

Advantages of FIT

  • Inexpensive
  • Covered by most health insurance
  • Can be completed in the comfort of your home
  • No drug or food restrictions
  • Collecting a stool sample may take less effort. FIT does not require samples from as many bowel movements.
  • More specific than FOBT. FIT only identifies human blood
  • Fewer samples are needed for testing.

Disadvantages of FIT

  • Only indicates if you already have cancer. FIT cannot identify precancerous polyps.

  • Will need to get a colonscopy if test is positive.

  • Patients may find the FIT test unpleasant to do.

  • May miss tumors that bleed in small amounts or not at all.

  • Costs more than a Fecal Occult Blood Test (FOBT)

  • Must be done yearly to be considered a fairly reliable alternative to colonoscopy.

Stool DNA test (sDNA)

Instead of looking for blood in the stool, this test looks for abnormal changes to the cells (DNA) in the colon. This is one of the new generation of tests which are being prepared for FDA approval. This test has not yet been approved by the FDA.

Screening interval is uncertain. Check with your healthcare professional.


  • Can detect polyps before they become cancer and can detect cancer as wel.l

  • No advance preparation or dietary restrictions.

  • Can be completed in the comfort of your home.

  • Non-invasive, painless and simple.

  • Results to date indicate that the sDNA test is highly accurate.


  • Not approved by the FDA yet and therefore not currently available.

  • Will need to get a colonoscopy if test is positive.

  • More expensive than the other stool tests.