It is normal for the stool to turn black after taking iron supplements. This is because after taking iron supplements, the iron will combine with hydrogen sulfide in the gastrointestinal tract, causing the stool to turn black in color. Usually, no special treatment is needed, and the black stool will disappear naturally after you stop taking iron. Long-term use of therapeutic iron supplements may cause nausea, vomiting, diarrhea, and black stools due to certain stimulation of the stomach and intestines. Usually bivalent iron preparations are used clinically, and commonly used oral iron supplements include ferrous sulfate and ferrous protein succinate. It is recommended that iron be taken orally between meals to reduce gastrointestinal side effects and to increase absorption. It is also recommended to take vitamin C, which can increase the absorption of iron.