Black loose stool is considered to be caused by food or medication factors, upper gastrointestinal bleeding, lower gastrointestinal bleeding, etc. 1. Food or drug factors: may be too much to eat dark pigmented food or food with high iron content, such as animal blood, liver, which leads to black stools, may also be caused by taking certain drugs, such as ferrous succinate, bismuth potassium citrate and so on. 2. Upper gastrointestinal bleeding: commonly seen in gastric and duodenal ulcers or cirrhosis of the liver causing rupture of the esophagogastric fundal varices and bleeding, upper gastrointestinal bleeding, this kind of patients bleeding is usually larger, blood accumulates in the intestinal tract, causing a black stool, usually manifested as a thin micro-volume of black stool. 3. Lower gastrointestinal bleeding: common in enteritis, intestinal polyps, colon tumors, colon inflammation, etc., bleeding in the intestinal tract for a long time after prolonged storage, after chemical changes, after pulling out is also black. When the disease is serious, it is easy to cause the intestinal mucosa to break, which causes bleeding, resulting in black stools, and often also accompanied by diarrhea. Therefore, when black loose stools occur, or accompanied by palpitations, pale, fatigue and other discomforts, it is recommended to consult a doctor in a timely manner, and actively treat the disease, so as to avoid delaying the condition.