Black stools are not caused by indigestion, but black stools should be alert to gastrointestinal bleeding, such as gastric perforation, rupture of the fundic vein, gastric cancer, etc. Some people are caused by dietary problems. Indigestion only affects the digestion of food in the stomach, the main symptoms of patients are bloating, stomach pain, nausea, vomiting, some patients will be accompanied by diarrhea, but under normal circumstances will not lead to black stool. Gastric ulcers, when aggravated, can even invade the entire stomach, and in severe cases can induce gastric perforation, which can cause upper gastrointestinal bleeding and black stools. In case of rupture of the fundic vein, massive bleeding will occur, which will not only be accompanied by vomiting blood, abdominal pain and other symptoms but also black stools. Gastric cancer is a malignant tumor, and when the disease is severe, it will not only invade the gastric mucosa, but also damage the blood vessels in the stomach wall, which will cause upper gastrointestinal bleeding and black stools. Eating foods containing iron in the diet may cause black stools because iron is oxidized in the digestive system.