A patient with low Mg (1.2 mg/dL) is at risk for refractory hypokalemia. What is the management?

• A. Administer potassium replacement
• B. Withhold all electrolytes
• C. Administer calcium gluconate
• D. Administer magnesium sulfate to correct deficiency; as Mg improves potassium repletion and prevents recurrence; monitor Mg and K+ levels

Answer: (D)

Magnesium status dictates potassium handling. When magnesium is low, the kidneys waste potassium and make it hard to raise the potassium level with potassium alone. The low Mg impairs the mechanisms that normally retain potassium (including the Na+/K+-ATPase function and renal potassium transport), so potassium replacement often remains ineffective until Mg is corrected. By administering magnesium sulfate to fix the deficiency, renal potassium loss decreases and potassium repletion becomes effective, reducing the chance of recurrent hypokalemia. After Mg is corrected, continue with potassium replacement and monitor both Mg and K+ levels to ensure sustained correction.