What action should the nurse take first when a patient on furosemide reports muscle weakness?

A. Increase fluid intake: Increasing oral hydration may improve overall fluid volume but does not specifically address the electrolyte imbalance caused by loop diuretics. Furosemide-induced muscle weakness is typically a manifestation of hypokalemia rather than simple dehydration. Encouraging fluids without assessing electrolyte status could potentially further dilute serum potassium levels through a shift. B. Reduce the furosemide dosage: Modifying a prescribed medication dosage is outside the independent scope of nursing practice and requires a provider's order. While the diuretic may be the cause of the symptom, the nurse must first gather objective data to justify a change. The priority is to assess the severity of the biochemical abnormality. C. Administer a potassium supplement: Providing a potassium supplement without a current laboratory value and a specific provider order is unsafe and potentially harmful. If the weakness is not due to hypokalemia, unnecessary supplementation could lead to life-threatening hyperkalemia and cardiac dysrhythmias. Data collection must precede pharmacological intervention in this clinical scenario. D. Check serum potassium levels: Furosemide inhibits the Na-K-2Cl symporter in the thick ascending limb, leading to significant potassium wasting and potential hypokalemia. Muscle weakness is a classic clinical sign of low potassium, which affects the resting membrane potential of excitable tissues. Obtaining a serum level is the critical first step to confirm the diagnosis.