A chronically alcoholic patient has potassium 3.2 mEq/L; after potassium supplementation, the potassium remains low. What is the most likely accompanying electrolyte abnormality?

A chronically alcoholic patient has potassium 3.2 mEq/L; after potassium supplementation, the potassium remains low. What is the most likely accompanying electrolyte abnormality?

• A. Hypomagnesemia
• B. Hypercalcemia
• C. Hyperkalemia
• D. Hypophosphatemia

Answer: (A)

Magnesium deficiency is the key factor here. In chronic alcoholism, low magnesium impairs the kidney’s ability to handle potassium, so potassium gets wasted in the urine even after supplementation. Magnesium is needed for proper Na+/K+-ATPase activity and for inhibiting distal potassium secretion; when Mg is low, these processes falter and potassium remains low despite giving more potassium. Replacing magnesium often allows potassium to rise, whereas without Mg correction, potassium repletion is ineffective. So the accompanying electrolyte abnormality you’d expect is hypomagnesemia. (Other common alcohol-related abnormalities like hypophosphatemia may occur, but they don’t explain the refractory potassium the way low magnesium does.)

Magnesium deficiency is the key factor here. In chronic alcoholism, low magnesium impairs the kidney’s ability to handle potassium, so potassium gets wasted in the urine even after supplementation. Magnesium is needed for proper Na+/K+-ATPase activity and for inhibiting distal potassium secretion; when Mg is low, these processes falter and potassium remains low despite giving more potassium. Replacing magnesium often allows potassium to rise, whereas without Mg correction, potassium repletion is ineffective. So the accompanying electrolyte abnormality you’d expect is hypomagnesemia. (Other common alcohol-related abnormalities like hypophosphatemia may occur, but they don’t explain the refractory potassium the way low magnesium does.)