Estimate calculated serum osmolality from sodium, glucose, and BUN in US units.
| Calculated osm | – |
Use this calculator for 2 × Na + glucose/18 + BUN/2.8, with sodium in mmol/L and glucose and BUN in mg/dl. Measured osmolality minus this value is the osmolar gap (alcohols, mannitol, and similar). Ethanol is not in this sketch. SI labs that already print glucose and urea in mmol/L need a different formula.
Na: Sodium, mmol/L.
Glucose: Glucose, mg/dl.
BUN: Blood urea nitrogen, mg/dl.
Calculated osm: Calculated osmolality, mOsm/kg.
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