Plasma osmolality

Normal human reference range of osmolality in plasma is about 275-299 milli-osmoles per kilogram.

To calculate plasma osmolarity use the following equation :

• = 2 x Na⁺ + Glucose +  BUN 
                                   18            2.8
  
  where [Glucose] and [BUN] are measured in mg/dL.

Simplifications are sometimes used:

• = 2[Na⁺] + [Glucose]/20 + BUN/3 - 2