"In marked hyperglycemia, ECF osmolality rises and exceeds that of
ICF, since glucose penetrates cell membranes slowly in the absence of insulin, resulting in movement of water out of cells into the
ECF. Serum Na concentration falls in proportion to the dilution of the ECF, declining 1.6
mEq/ L for every 100 mg/dL (5.55 mmol/L) increment in the plasma glucose level above normal. This condition has been called translational hyponatremia because no net change in total body water
(TBW) has occurred. No specific therapy is indicated, because Na concentration will return to normal once the plasma glucose concentration is lowered."
= Measured sodium + (((Serum glucose - 100)/100) x 1.6)
Alternatively (equivalent equation):
= Measured sodium + 0.016 x (Serum glucose - 100)