Black stool is a normal phenomenon due to the oxidation of ferrous sulfate to trivalent iron in the intestinal tract, resulting in black stool color. In addition to ferrous sulfate, we commonly use ferric succinate solution or polysaccharide iron complex capsules, etc., after oral administration will appear black stool color performance, is not a disease, no special treatment. However, it should be emphasized that it should be distinguished from the black stool of gastrointestinal bleeding. If the patient is suffering from gastrointestinal bleeding, in addition to black stool symptoms, it will also be accompanied by upper abdominal symptoms, such as epigastric pain, epigastric discomfort, acid reflux, heartburn, nausea, vomiting, as well as peripheral circulatory disorders, such as weakness, night sweats, panic attacks, etc. At this time, the patient should immediately go to the hospital to improve the gastroscopy to clarify the diagnosis.