Case of the Month #2 - ethylene glycol ingestion

Published 03/02/2022

What is osmolal gap and what causes increased osmolal gap?

Osmolal gap = measured serum osmolality – calculated osmolality

Calculated osmolality = (2 x [Na]) + [Glucose] + [Urea] (all in mmol/L)

A normal osmolal gap is < 10mOsm/kg

When the osmolal gap is increased (>10 mOsm/kg), causes to consider include:

  • Alcohols e.g. ethanol, methanol, ethylene glycol 
  • Sugars e.g. mannitol 
  • Lipids e.g. hypertriglyceridaemia 
  • Proteins e.g. Waldenstrom macroglobulinaemia