Which lab value indicates risk of hyponatremia in a patient receiving diuretic therapy?

• A. Potassium 4.0 mEq/L
• B. Sodium 128 mEq/L
• C. Creatinine 1.0 mg/dL
• D. Sodium 135 mEq/L

Answer: (B)

Hyponatremia risk with diuretic therapy centers on how these drugs disrupt sodium and water balance. Diuretics can push sodium out in the urine, and in some cases promote relative water retention, especially if fluid intake is high or ADH is elevated. A serum sodium of 128 mEq/L is below the normal range (135–145 mEq/L) and shows hyponatremia, which is the lab finding of concern in this context. The other values don’t indicate hyponatremia: potassium at 4.0 is normal, creatinine at 1.0 mg/dL suggests normal kidney function, and sodium at 135 mEq/L is not frankly hyponatremic. So the low sodium level is the indicator that the patient on diuretics is at risk for hyponatremia. Monitor sodium closely, reassess diuretic therapy, and watch for symptoms such as confusion or seizures.