Final answer:
The nurse should monitor serum potassium levels before administering hydrochlorothiazide.
Step-by-step explanation:
Prior to administering hydrochlorothiazide, the nurse should monitor serum potassium levels. Hydrochlorothiazide is a diuretic medication often used to treat conditions such as hypertension and edema. It works by increasing urine production, leading to increased excretion of sodium and water. However, it can also cause depletion of potassium, so monitoring potassium levels is important to ensure proper balance.