Serum Osmolality

Sodium (Na):	mmol/L
(optional) Potassium (K):	mmol/L
BUN:	mg/dl
Glucose:	mg/dl

Serum Osmolality =	mOsm/kg
Normal Range =	285 - 295 mOsm/kg

Serum Osmolality = (2 x 
      (Na + K)) + (BUN / 2.8) + (glucose / 18)