Drinking coffee in moderation occasionally will not cause black stools, but if drinking a lot of coffee for a long time induces gastric diseases and complicates gastric bleeding, it can cause black stools. The common causes of black stools include dietary factors such as eating animal blood, green leafy vegetables and other iron-rich foods, taking iron, bismuth and other medications; peptic ulcer combined with bleeding, rupture of the esophagogastric varices, bleeding and other diseases induced by upper gastrointestinal hemorrhage and other factors. Therefore, drinking coffee occasionally will not cause black stools, but if you drink too much coffee for a long time may promote the secretion of gastric acid, gastric mucosa long-term stimulation by high concentration of gastric acid will cause gastric mucosal lesions, when the lesions further development of gastric hemorrhage will lead to black stools. If you suspect that the symptoms of black stool are caused by pathological factors such as gastrointestinal bleeding, it is recommended to go to the hospital for medical treatment.