During refeeding in anorexia nervosa, which electrolyte disturbance is of particular concern?

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

Answer: (C)

Refeeding syndrome occurs when nutrition is restarted after a period of severe malnutrition. The moment carbohydrates are added, insulin rises and drives phosphate, potassium, and magnesium from the blood into cells to support new glucose metabolism. Phosphate is especially critical because it is needed for ATP production and many energy-demanding processes. When serum phosphate falls rapidly, cells and organs can’t maintain energy-dependent functions, causing muscle weakness, respiratory failure from diaphragmatic weakness, cardiac dysfunction and arrhythmias, and even hemolysis or rhabdomyolysis. This is why hypophosphatemia is the electrolyte disturbance of particular concern during refeeding in anorexia nervosa.

Other shifts can occur, but they’re not the hallmark concern in this scenario. Potassium often declines due to cellular uptake, not rises, so hyperkalemia is unlikely. Hyponatremia and hypercalcemia can occur in some contexts, but they’re not the primary or most characteristic issue during the early phase of refeeding.