Delirium in a patient taking a thiazide diuretic may indicate which electrolyte disturbance?

• A. Hyperkalemia
• B. Hypercalcemia
• C. Hypomagnesemia
• D. Hyponatremia

Answer: (B)

Thiazide diuretics raise calcium reabsorption in the distal tubule, which reduces urinary calcium excretion and can lead to hypercalcemia. Hypercalcemia, in turn, can cause neuropsychiatric symptoms such as delirium, especially in older adults. So when delirium appears in a patient taking a thiazide, hypercalcemia is the most consistent electrolyte disturbance to consider. (Hyponatremia and other electrolyte effects can occur with thiazides, but hypercalcemia is the classic culprit linked to this drug class in this clinical vignette.)