Black stools may be caused by eating a certain amount of black food or animal blood products, or it may be due to gastrointestinal bleeding. 1. Eating black food or animal blood products: some black food in the black material is difficult to be digested and decomposed, dispersed and mixed in the feces to reach a certain amount of feces will be black, so it looks like the stool is black, in addition to animal blood products in the oxidation of iron in the digestive tract will be black state. 2. Gastrointestinal bleeding: gastric ulcers, duodenal ulcers, small intestinal bleeding, etc. can lead to human blood into the gastrointestinal tract, the iron in the blood is oxidized to black, and mixed in the feces will also look black. If you exclude food causes, black stools should be recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.