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, iron succinate oral solution and so on. This is due to the oxidation of iron into trivalent iron in the intestinal tract and mixing with stool. If the patient does not have obvious symptoms of abdominal pain, bloating, acid reflux, heartburn, nausea, vomiting, etc., the patient does not need special treatment and the color of stool 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 to improve gastroscopy to further clarify the diagnosis.