Small quantities of blood in the feces that are not apparent to the eye and are detectable only by special laboratory tests. If occult blood is detected it suggests that there is bleeding somewhere in the gastrointestinal tract, and further tests will be necessary. Since the bleeding may be intermittent, the laboratory tests have to show no occult blood in the stool on several occasions before the physician can be fairly certain that there is no bleeding in the gastrointestinal tract. Blood from ingested meat (even if cooked) can give a positive result to the test; thus, the patient should go on a meat free diet for about three days before the test.