If a client reports black stool, which medication is most likely responsible for this side effect?

The presence of black stool, also known as melena, can often indicate gastrointestinal bleeding or the consumption of certain substances or medications. In this case, ferrous sulfate is the medication most likely to cause black stool as a side effect.

Ferrous sulfate is an iron supplement commonly prescribed for iron deficiency anemia. When taken, it can react with the digestive processes and the enzymes in the gastrointestinal tract, turning the stool a dark color. This is due to the iron itself being poorly absorbed, leading to excess being present in the intestines, which in turn can produce this characteristic change in stool color.

Recognizing this side effect is crucial in clinical practice, as it helps differentiate between a benign side effect of a commonly used medication and possible signs of serious underlying conditions, such as gastrointestinal bleeding that may require immediate medical attention.