Patient Instructions: Fecal Occult Blood Test

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Patient Instructions


Fecal Occult Blood Test


A fecal occult blood (FOBT) test finds blood in the stool by placing a small sample of stool on a chemically treated card, pad, or cloth wipe. Then a special chemical solution is put on top of the sample. If the card, pad, or cloth turns blue, there is blood in the stool sample.

If your doctor has prescribed a fecal occult blood test then you will need to restrict your diet. Fasting for a fecal occult blood test is usually less restrictive than fasting for other types of tests, but you need to follow your doctor's recommendations in order to get the most reliable results.

First, let your doctor know if you have bleeding gums before you begin fasting for a fecal occult blood test. Bleeding gums can cause you to swallow blood and therefore cause the test to read a false positive.

Follow a high-fiber diet starting two days before and continuing throughout the test period. Avoid eating red or rare meat. Foods like beef contain hemoglobin, which is what the fecal occult blood test is testing for. If the fecal occult blood test is not specifically designed to located human hemoglobin, then the test may read a false positive if you have eaten meat. Meats such as well-cooked chicken, turkey or tuna are acceptable.

Limit your vitamin C intake. Too much vitamin C can lead to a false negative result in the fecal occult blood test, so put down the orange juice until you've completed the fecal occult blood test. Caution: Some iron supplements contain Vitamin C which may effect the testing. Avoid eating fruits and vegetables containing high peroxidase activity, which include turnips, cauliflower, red radishes, broccoli, cantaloupe, horseradish and parsnips. Other than those fruits and vegetables, eating generous amounts of both raw and cooked vegetables, including lettuce, corn, spinach, celery, carrots, apples and prunes are encouraged. Grains and moderate amount peanuts and popcorn are acceptable.

Talk to your doctor about the medications you are taking. Some medications, like aspirin, steroids, and non-steroidal anti-inflammatory drugs can cause intestinal bleeding and therefore cause a false positive result, so you may need to omit certain medications while fasting for the fecal occult blood test. Avoid these for seven days prior to and during the test if possible.

Avoid rectal preparations two days prior and during the testing.

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Dominican Hospital
1555 Soquel Dr
Santa Cruz, CA 95065
(831) 462-7700