Fecal occult blood means that the appearance of the stool is normal to the naked eye, but blood cells can be found in the stool through laboratory tests. The main causes of fecal occult blood are the following: first, the consumption of animal blood, after eating animal blood will have the possibility of positive fecal occult blood, it is recommended to recheck after a week or so. The second, diseases of the digestive tract, such as gastric ulcers, duodenal ulcers, when the ulcers destroy the small blood vessels, there will be positive fecal occult blood suggests that the original disease should be treated. Thirdly, gastrointestinal tumors, such as gastric cancer, are more common, and long-term positive fecal occult blood must be alert to gastric cancer, and gastroscopy should be conducted in time to clarify the cause of fecal occult blood.