Calculate serum osmolality using the sample’s sodium, blood urea nitrogen (BUN), glucose and ethanol levels.
Formula:
Serum osmolality = 2*Na + BUN/2.8 + glucose/18 + alcohol/3.7
Normal range = 275 to 295 mOsm/kg
Principle:
Osmolality is a special variation of molality, and is a measure of the number of dissolved, osmotically active, particles in a fluid, and is an indicator of your water-electrolytes balance. In the case of serum osmolality, we measure substances such as sodium, urea nitrogen, glucose, alcohol, and potassium. Sodium is the main component of serum osmolality, whereas potassium can be omitted, as it has a minuscule influence.
