Black stools may be caused by diet and medication, etc. If you have recently eaten animal blood or offal, beef, etc., your stools may turn black. 1. Diet: If you have recently eaten animal blood or offal, beef and other foods, can lead to black stools, because these foods contain high iron content, the iron contained in the human intestinal tract will form a black substance, so that the color of the stool becomes black, this is a normal phenomenon, it is not due to disease and caused by the body, the body is all normal, without any discomfort. 2. Drugs: eat iron supplements such as ferrous sulfate, black stool is often due to iron is not fully absorbed mixed in the feces is oxidized with the feces out of the body and caused by this situation is a very normal physiological phenomenon, it is not due to disease, the body is normal, there is no discomfort. If you have any discomfort, it is recommended that you consult a doctor in a timely manner and actively cooperate with the doctor for treatment.