In older adults receiving aggressive nutrition support, which electrolyte abnormality is most commonly associated?

• A. Hyperkalemia
• B. Hypocalcemia
• C. Hypermagnesemia
• D. Hypophosphatemia

Answer: (D)

Refeeding syndrome is the key concept here: when malnourished individuals, such as older adults with depleted stores, receive aggressive nutrition, a surge of insulin drives phosphate into cells to support new energy production. This rapid intracellular shift can cause a drop in serum phosphate, making hypophosphatemia the most common electrolyte abnormality seen with aggressive nutrition support. Low phosphate can impair muscle (including diaphragm and cardiac muscle), red and white blood cell function, and overall energy metabolism, so monitoring and correcting phosphate is critical as nutrition is advanced. Thiamine should be given beforehand, and rates of nutrition should be started low and increased gradually while tracking electrolytes. While shifts in potassium and magnesium can also occur, the characteristic and most frequent finding in this situation is hypophosphatemia.