Frequent and black stools are usually considered to be caused by dietary factors, medication factors, gastrointestinal bleeding and so on. 1. Dietary factors: patients with increased stool frequency and black stools may be related to their recent diet, for example, when consuming too much duck blood, animal offal and other iron-rich foods, the unabsorbed iron will react with sulfur under the action of intestinal bacteria and gastric acid to form black ferrous sulfide, which will lead to black stools. 2. Drugs: If the patient has recently taken some drugs, such as iron, colloidal bismuth pectin capsules, etc., it will also cause black stools. 3. Gastrointestinal bleeding: if the patient has gastrointestinal bleeding, due to the iron in the blood through the intestinal reaction, it will form black ferrous sulfide, and there will be an increase in the number of bowel movements, and the color of the stool becomes black, clinically there are a lot of diseases that can cause bleeding in the gastrointestinal tract, such as peptic ulcers, esophagogastric fundal varicose veins and other common diseases. There may be other reasons for frequent and black stools, so it is recommended to consult a doctor in time to clarify the cause of the disease and standardize the treatment in order to reduce the adverse effects of the disease.