Online Clinical Calculator: Serum Osmolality
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Na
mEq/L
Glucose
mg/dL
BUN
mg/dL
Ethanol
mg/dL
Serum Osmolality =
mOsm/kg H
2
0
Osmolality = (2)(Na) + Glucose/18 + BUN/2.8 + EtOH/4.6
This formula accounts for most common osmotically active solutes. Ethanol value is optional.
Normal is 285-290 mOsm/kg H
2
0
Online Clinical Calculator: Serum Osmolality
