Osmolal Gap Calculator

Serum Na
Serum Glucose
Serum BUN
Serum Ethanol
Measured Osm
Calculated Osm
Osmolal Gap
Decimal Precision:
CalculatedOsm = (SerumNa * 2) + (SerumGlucose / 18) + (SerumBUN / 2.8) + (SerumEthanol / 4.6)
OsmolalGap = MeasuredOsm - CalculatedOsm
  • A significant Osmolal Gap can indicate intoxication by methanol, ethylene glycol or isopropanol.
  • The magnitude of this gap can be correlated with the concentration of these intoxicants.
  1. Bhagat CI, Garcia-Webb P, Fletcher E, et. al. Calculated vs measured plasma osmolalities revisited. Clin Chem. 1984 Oct;30(10):1703-5.
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