Which mechanism explains how insulin lowers potassium during hyperkalemia treatment?

• A. Increases renal excretion of potassium
• B. Causes potassium retention by blocking secretion
• C. Reduces intestinal potassium absorption
• D. Promotes potassium shift into cells via Na+/K+-ATPase

Answer: (D)

Insulin lowers extracellular potassium by stimulating the Na+/K+-ATPase pump on cell membranes. When insulin is present, this pump moves potassium from the blood into cells (especially muscle and liver) in exchange for sodium, rapidly reducing the potassium level in the blood. This intracellular shift is the main reason insulin is used acutely in hyperkalemia management, typically taking effect within minutes to an hour and lasting for several hours.

This mechanism is distinct from increasing renal excretion or reducing intestinal absorption, and it does not cause potassium retention. The reason insulin is given with glucose in practice is to prevent hypoglycemia while it drives potassium into cells.