Calculator

Osmolal gap

New

Measured − calculated osmolality. Raised in toxic alcohol poisoning.

mOsm/kg
mmol/L
mg/dL
mg/dL

Osmolal gap

29 mOsm/kg

Raised: consider methanol, ethylene glycol, ethanol, mannitol

Normal (< 10)
Raised: consider methanol, ethylene glycol, ethanol, mannitol

Formula

measured - (2 * na + glucose / 18 + urea / 6)

References

  1. Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med 1999;106:399-403.

Used in

High anion gap metabolic acidosisOsmotherapy: mannitol vs hypertonic salineInitial approach and toxidromesMethanol and other toxic alcohols

Calculators support, not replace, clinical judgement. Check inputs and units, and confirm doses with your unit protocol.