Which statement best describes the relationship between magnesium and potassium repletion?

• A. Hypomagnesemia impairs potassium repletion and prolongs correction
• B. It accelerates potassium loss
• C. It raises calcium levels
• D. It is unnecessary

Answer: (B)

Magnesium status governs how well potassium can be repleted. When magnesium is low, correcting potassium becomes difficult and correction is often slow or incomplete because the kidneys waste potassium and cellular uptake is impaired. Magnesium is a necessary cofactor for Na+/K+-ATPase, so low magnesium reduces the pump’s function and hinders intracellular potassium accumulation. In the kidney, hypomagnesemia promotes potassium loss through renal channels, so even with potassium supplements, much of the potassium is lost in urine until magnesium is replenished. Therefore, to reliably correct a potassium deficit, you must replete magnesium (often alongside potassium) to restore both cellular uptake and renal handling. This is why the relationship is best described by the need to address magnesium to achieve effective potassium repletion.