What mechanism explains hypokalemia during insulin therapy?

• A. Potassium shifts from extracellular to intracellular
• B. Potassium shifts from intracellular to extracellular
• C. Decreased renal excretion
• D. Increased potassium intake

Answer: (A)

Insulin drives potassium into cells, which lowers the amount of potassium in the bloodstream. It does this by activating the Na+/K+-ATPase pump, increasing the transport of potassium from the extracellular space into cells such as muscle and liver. As a result, serum potassium falls, producing hypokalemia when insulin therapy is started or continued. This effect is about distribution of potassium between compartments rather than actual loss from the body, though total body potassium can be depleted in conditions like diabetic ketoacidosis. The other ideas—potassium staying in the blood longer because of reduced renal excretion or getting more potassium from intake—don’t account for the rapid drop seen with insulin, since insulin’s primary action here is cellular uptake of potassium, moving it from outside the cells into the interior.