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Thiazide-induced hypokalemia — USMLE Step 3 MCQ

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ModerateAmbulatory Medicine / Primary CareThiazide-induced hypokalemiaUSMLE Step 3

A 59-year-old woman starts hydrochlorothiazide for hypertension. Two weeks later she develops weakness and muscle cramps. Laboratory studies show sodium 139 mEq/L, potassium 3.0 mEq/L, bicarbonate 31 mEq/L, and creatinine 0.9 mg/dL. Which of the following is the most likely explanation for this patient's findings?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Increased distal sodium delivery causing renal potassium loss

Thiazides increase distal sodium delivery, promoting potassium and hydrogen ion secretion with hypokalemic metabolic alkalosis.

Reference: USMLE Step 3 Content Outline; hypertension pharmacology