Hydrochlorothiazide can decrease potassium. True or False?

• A. Decreases potassium
• B. Increases potassium
• C. No effect on potassium
• D. Increases calcium

Answer: (A)

Thiazide diuretics, like hydrochlorothiazide, can lower potassium. They block the Na-Cl cotransporter in the distal convoluted tubule, so less Na+ is reabsorbed there. More sodium reaches the collecting duct, where Na+ reabsorption is coupled to potassium (and hydrogen ion) secretion. This increased K+ excretion in the distal nephron leads to hypokalemia. There’s also an effect on calcium: hydrochlorothiazide increases calcium reabsorption in the distal tubule, which lowers urinary calcium. The potassium-lowering effect is the key point for this question, making the statement true.