Serum Osmolality Calculator
Calculate serum osmolality including optional ethanol contribution using the extended Ohm formula.
How to Use the Serum Osmolality Calculator
- Enter serum sodium (Na⁺) in mEq/L.
- Enter serum glucose in mg/dL.
- Enter BUN in mg/dL.
- Enter serum ethanol in mg/dL (or 0 if not applicable).
- Click Calculate to see osmolality and interpretation.
使用例
- •Calculating osmolar gap in suspected toxic alcohol ingestion.
- •Evaluating altered mental status in the emergency department.
- •Teaching clinical toxicology and nephrology concepts.
計算式
Formula: Osm (mOsm/kg) = 2×Na + glucose/18 + BUN/2.8 + ethanol/4.6. Set ethanol to 0 if not applicable.
よくある質問
What is the osmolar gap?
The osmolar gap is the difference between measured osmolality (by freezing point depression) and calculated osmolality. A gap > 10 mOsm/kg suggests unmeasured osmoles such as ethanol, methanol, ethylene glycol, or isopropanol.
Why is ethanol divided by 4.6?
Ethanol's molecular weight is 46 g/mol. Dividing the ethanol level in mg/dL by 4.6 converts it to mmol/L (mOsm/kg contribution).
Disclaimer
For educational purposes only. Always confirm with laboratory-measured osmolality. This calculator does not replace clinical assessment or toxicology workup.