Black poop can be caused by dietary factors, medications, and gastrointestinal bleeding. 1. Dietary factors: Eating black food, such as black fungus, black beans, black sesame, etc. or eating animal blood products such as chicken blood or duck blood can cause the color of stool to turn black. 2. Drugs: taking iron supplements (ferrous succinate, etc.), bismuth (bismuth potassium citrate, etc.), etc., can cause the color of stool to become black. 3. Gastrointestinal bleeding: for example, bleeding gastritis, gastric ulcer, duodenal ulcer, esophageal ulcer bleeding, etc., the blood stays in the intestinal tract for a long time through the oxidation, resulting in the black color of the stool. If the black color of stool persists, it is recommended to consult a doctor in time to find out the cause of the disease and treat it as soon as possible.