After drinking black coffee it is possible that melanin cannot be fully metabolized and the color of the stool deepens and looks like black. There may also be gastritis and other diseases, black coffee stimulates mucous membrane bleeding, causing black stools. 1. Drinking black coffee generally does not appear black stool, due to black coffee melanin is relatively heavy, drinking a lot of black coffee, pigment can not be fully metabolized, out of the body, there may be a darker color of stool, usually dark brown, looks like black. In this case, there are usually no other uncomfortable symptoms, and the color of stool can return to normal after stopping drinking black coffee. 2. If you have gastritis, gastric ulcer and other diseases, black coffee flavor is generally more bitter, will stimulate the damaged gastrointestinal mucosa, resulting in gastrointestinal bleeding. The red blood cells in the blood under the action of digestive juices and other substances undergo a chemical reaction, the color will be black, black stools, and at the same time there may be abdominal distension. Symptoms such as abdominal pain. Endoscopy and fecal occult blood test can be done to check for bleeding. The appearance of the phenomenon discharge drinking a lot of black coffee caused by deepening the color of the stool and other physiological reasons, but also may be other reasons, should be timely consultation, under the guidance of the doctor to identify the causes, and reasonable treatment.