A patient is taking bismuth subsalicylate to prevent diarrhea. The nurse performing an assessment notes that the patient's tongue is black. What will the nurse do?

A. Request an order for liver function tests to evaluate for hepatotoxicity: Bismuth subsalicylate is not associated with hepatotoxicity, and a black tongue is not indicative of liver dysfunction. There is no need for liver enzyme testing based solely on tongue discoloration. B. Withhold the drug, because this is a sign of bismuth overdose: A black tongue is not a sign of overdose but rather a known harmless side effect due to the interaction of bismuth with sulfur in the saliva. Discontinuation is not warranted. C. Assess further for signs of gastrointestinal (GI) bleeding: Although bismuth can cause dark stools, which may resemble melena, a black tongue specifically is not an indication of GI bleeding. Unless there are other signs, further assessment is unnecessary here. D. Reassure the patient that this is an expected side effect of this drug: Bismuth subsalicylate often causes temporary blackening of the tongue or stool due to its chemical composition. This effect is benign and reversible, and reassurance is the appropriate nursing response.