Usually, after taking iron supplements orally, the stool will be black in color. The commonly used iron supplements are ferrous succinate, ferrous sulfate or polysaccharide complex, oral iron succinate solution and so on. This is due to the oxidation of iron to trivalent iron in the intestine and mixing with stool. If the patient does not have obvious abdominal pain, bloating, acid reflux, heartburn, nausea, vomiting and other symptoms, the patient does not need special treatment and the stool color will return to normal after stopping the drug. If the patient has black stool and the above mentioned symptoms, it is not excluded that the patient has gastrointestinal bleeding, so it is recommended that the patient should immediately go to the hospital for gastroscopy to further clarify the diagnosis.