Hyperglycemia-Induced Hyponatremia — Calculation of Expected Serum Sodium Depression

Abstract

FOR at least 1/4 century clinicians have recognized that hyperglycemia depresses serum sodium concentration.1 Since glucose is largely restricted to extracellular fluid, an increase in its concentration moves water out of cells, causing dilution of extracellular solute. It is useful to assess the expected sodium decrease for a given glucose level, because deviations from such a predicted value establish the diagnosis of hyponatremia or hypernatremia that may require therapy in addition to correction of the hyperglycemia. Most clinicians use the rule of thumb that there is a 2.8 mEq per liter decrease in serum sodium for every 100 mg per . . .