Black stools may occur clinically when taking some iron, bismuth, and some herbal medicines. Ferrous sulfate and ferrous succinate are commonly used for iron, and bismuth and bismuth are commonly used for bismuth pectin and gastric bismuth, and black stools may occur during taking the above drugs. However, if accompanied by stomach discomfort, such as nausea, acid reflux, belching, indigestion, abdominal pain, dizziness, weakness and other uncomfortable symptoms, patients should go to the hospital for systematic examination to exclude gastrointestinal bleeding. In addition, in addition to observing the color of the stool during medication, attention should also be paid to the volume of defecation, the nature and smell of the stool to prevent masking the disease, especially for upper gastrointestinal bleeding with predominantly black stools, which must be screened and treated under the guidance of a doctor.