What is the effect of insulin on potassium levels?

Insulin plays a crucial role in the metabolism of various substances, including potassium. When insulin is released, it facilitates the movement of potassium from the extracellular fluid (the serum) into the cells. This action is primarily due to insulin stimulating the activity of the sodium-potassium ATPase pump, which actively transports potassium ions into the cells while moving sodium ions out.

As a result, when insulin promotes this uptake, it effectively leads to a decrease in serum potassium levels, which is particularly significant in clinical settings such as during the treatment of hyperkalemia (elevated potassium levels in the blood). This mechanism is utilized when managing certain conditions, as administering insulin can help lower high potassium levels and prevent complications associated with hyperkalemia.

Therefore, the correct answer accurately reflects the physiological action of insulin on potassium levels in the body.