Final answer:
Nurses should inform the healthcare provider if a bipolar disorder client on lithium is prescribed furosemide, due to the risk of lithium toxicity from increased lithium levels in the blood.
Step-by-step explanation:
The subject of this question is medicine, specifically related to bipolar disorder and medication interactions. When a client with bipolar disorder is taking lithium, the nurse should notify the health care provider if the client is prescribed furosemide. Furosemide is a diuretic that can lower the renal clearance of lithium, potentially leading to increased lithium levels in the blood and the risk of lithium toxicity. It is important to closely monitor such medication combinations and adjust dosages accordingly to ensure patient safety and effective treatment.