An occult blood test in the stool is a chemical test done to detect the presence of blood not visible (occult) to the naked eye. It is done as small blood loss from some diseases in the colon like polyps, inflammatory states, or cancers can occur over a period of time and the patient may not be aware of it. This often comes to light when a patient is found to be anaemic. Three specimens of stool collected on 3 different days are tested. Prior to the test, individuals are asked not to eat some foods (like meat) or take certain drugs like iron, aspirin, vitamin C etc. as this would result in a false positive test result. If the test is positive, a colonoscopy is advised to exclude diseases like polyps, inflammations, abnormal blood vessels or cancer of the colon. If this is normal, then the site of blood loss could be the stomach or the small intestine and your doctor will advise you appropriately.