Feces that are black may be related to factors such as diet, medication, and disease. For example, eating food such as animal blood products or animal liver; for example, taking drugs such as iron and bismuth; for example, diseases such as acute gastritis, gastric ulcer and cirrhosis of the liver. 1. Dietary causes: such as eating animal blood products or liver. This kind of food is rich in iron ions, which can lead to black stools under the oxidizing effect of the intestines. 2. Drug causes: such as taking iron or bismuth agents, such as ferrous fumarate, bismuth potassium citrate, etc., usually no discomfort. After stopping the medication, it can gradually return to normal. 3. Disease causes: such as acute gastritis with nausea, vomiting, abdominal pain and other symptoms; such as gastric ulcer with stomach pain after meals, stomach bloating and other symptoms; such as cirrhosis of the liver can have jaundice, fatigue, ascites and other symptoms. There are many other reasons for dark stools, such as blood diseases, digestive tract tumors, etc. For dark stools, it is recommended to consult a doctor to clarify the cause.