Osmolal Gap
Info
Meas_Osm
Na
unit mg/dL mmol/L
BUN
unit mg/dL mmol/L
Glucose
unit mg/dL mmol/L
R e s u l t s
mOsm/kg serum H20
? ? ?
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Info
Osmolal Gap
Osmolal Gap= Measured Osm - Calculated Osm =

Meas Osm - [(2*Na)+(BUN/2.8)+(Glu/18)]

 

Normal < 10 mOsm/kg serum H20

 

Useful to group anion gap acidoses

 

Elevated gap: presence of significant amounts of unmeasured osmotically active solutes, incl. ethanol, methanol, paraldehyde, ethylene glycol, etc.

 

When Osmolal Gap due to ethanol:

Blood Alcohol Level (mg/dL)= 4.3 * Osm Gap.