Black-red color of bleeding stool is common in digestive system diseases, such as peptic ulcer combined with bleeding, digestive tract perforation combined with bleeding, ruptured esophagogastric fundic varices bleeding, tumor lesions, intestinal diseases, etc. The color of the blood depends on the location of gastrointestinal bleeding, the amount of bleeding, and the time the blood stays in the gastrointestinal tract. Bleeding accompanied by bleeding from the skin, mucous membranes, or other organs is mostly seen in hematologic diseases and other systemic diseases, such as leukemia and diffuse intravascular coagulation. Bleeding with systemic symptoms, such as dizziness, vomiting of blood, generalized pallor of skin and mucous membranes, shock, etc., are considered digestive system diseases. Recent oral administration of blood and iron supplements, drugs to protect the gastric mucosa, such as bismuth potassium citrate, and consumption of blood products such as hairy blood, may also cause physiological stool color changes, and it is recommended to seek medical examination to exclude physical diseases.