mmol/L
⚕️ For clinical reference only. Not a substitute for professional judgment.
Serum Osmolality Calculated
Calculated plasma osmolality. Compare to measured osmolality to identify osmolar gap — key in toxic alcohol ingestion.
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Enter values
Awaiting sodium (minimum required).
UK/SI Formula (mmol/L)
mmol/L
mmol/L
Formula
UK/SI: 2×Na + Glucose + Urea (all mmol/L)
Normal: 275–295 mOsm/kg
Osmolar Gap = Measured − Calculated
Normal gap: <10 mOsm/kg
Gap >10 → suspect ethanol, methanol, ethylene glycol, isopropanol
Normal: 275–295 mOsm/kg
Osmolar Gap = Measured − Calculated
Normal gap: <10 mOsm/kg
Gap >10 → suspect ethanol, methanol, ethylene glycol, isopropanol
When to use
- Suspected toxic alcohol ingestion (methanol, ethylene glycol)
- HHS — glucose typically >30 mmol/L, osmolality >320
- DKA — assess severity and monitor treatment
- Hyponatraemia workup — differentiates iso/hyper-osmolar states