Black stool formation is generally associated with disease factors such as gastrointestinal bleeding, dietary factors, medication factors and other reasons. 1. Disease factors: such as peptic ulcer, digestive tract tumor, esophageal varices and other diseases will destroy the red blood cells in the body, hemoglobin in the intestinal tract and sulfide combined to form ferrous sulfide, so that the stool black, thus appearing in the phenomenon of black stool formation. 2. Dietary factors: Eating too much meat, animal liver, animal blood, dark-colored food, etc. may lead to black stools and the phenomenon of black stool formation. 3. Drug factors: bismuth and iron components in some drugs will have chemical reactions in the gastrointestinal tract, such as colloidal bismuth pectin capsules, bismuth citrate potassium capsules and other drugs, which will lead to the phenomenon of black stool formation. It is recommended that patients go to the hospital in a timely manner to consult a doctor, and actively treat the cause of the disease after clarification.