In hyperkalemia, what is the mechanism of action of intravenous regular insulin with glucose?

• A. It increases urinary excretion of potassium
• B. It shifts potassium from extracellular to intracellular compartments
• C. It increases intestinal potassium absorption
• D. It inhibits potassium uptake by cells

Answer: (B)

The key idea is that insulin lowers potassium in the blood by moving it into cells. When regular insulin is given with glucose, it activates the Na+/K+-ATPase pump on cell membranes, which pumps potassium from the extracellular space into the intracellular compartment. This shifts potassium into cells quickly, reducing the high serum potassium seen in hyperkalemia.

The glucose is added to prevent insulin-induced hypoglycemia, allowing the potassium-shifting effect to occur safely. This action is rapid but temporary; potassium can rebound into the blood as insulin wears off, so other treatments may be needed for lasting control.

Other options don’t fit because insulin’s immediate action is not to increase potassium excretion by the kidneys, nor to increase intestinal absorption, and it does not inhibit cellular potassium uptake—in fact, it facilitates uptake.