Which laboratory value would the nurse report to the health care provider as a potential adverse response to hydrochlorothiazide?

• A. Sodium level of 140 mEq/L
• B. Fasting blood glucose level of 140 mg/dL
• C. Calcium level of 9 mg/dL
• D. Chloride level of 100 mEq/L

Answer: (D)

When a patient takes a thiazide diuretic like hydrochlorothiazide, the drug acts in the distal tubule to block Na-Cl reabsorption, leading to the loss of sodium and chloride in the urine. This electrolyte effect is a common source of adverse responses, and monitoring electrolytes is a key part of nursing care with these medications. Among the common lab changes, chloride disturbance is a direct reflection of the drug’s action on the distal nephron, so reporting a chloride abnormality to the provider is appropriate when assessing potential adverse effects.

In this scenario, the chloride level is the value to flag because it directly signals a disturbance in chloride balance that can accompany thiazide use. While normal sodium and calcium values are reassuring and a fasting glucose of 140 mg/dL can occur with thiazides, the chloride abnormality is most closely tied to the drug’s expected electrolyte impact. If the chloride value is outside the patient’s baseline—or outside the lab’s reference range—it would warrant reporting and evaluation for a possible adverse effect of hydrochlorothiazide.