Black feces may be caused by eating black food, drugs, upper gastrointestinal bleeding and other factors. 1. Eating black food: when patients consume a large amount of food carrying pigment or iron ions in a short period of time, it will lead to pigment mixing into feces, which will make the patients have the manifestation of black feces, such as mulberry, animal blood products and so on. 2. Drugs: generally patients taking bismuth or iron, such as ferrous succinate, bismuth potassium citrate, etc., will have black stool. It is because the unabsorbed iron can form black iron sulfide in the intestine. 3. Upper gastrointestinal bleeding: when suffering from upper gastrointestinal bleeding, blood will enter the feces with the intestines, which may also cause black stool. There may also be other reasons for the symptoms of black feces, so it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment.