Which electrolyte disturbance is commonly associated with diuretic use?

• A. Hypernatremia
• B. Hyponatremia
• C. Hypokalemia
• D. Hyperkalemia

Answer: (C)

Diuretics raise urine output by blocking sodium reabsorption at parts of the nephron, which leads to more sodium reaching the distal tubule and collecting duct. There, sodium is reabsorbed in exchange for potassium being secreted into the urine. This increased potassium loss causes low potassium levels in the blood. This pattern is especially true for loop and thiazide diuretics, making hypokalemia the classic electrolyte disturbance associated with diuretic use. (Some diuretics, called potassium-sparing diuretics, can raise potassium instead, but the common scenario with most diuretics is low potassium.)