Calculated Serum Osmolality
Estimated serum osmolality from sodium, glucose, and BUN.
What is Calculated Serum Osmolality?
Estimated serum osmolality from sodium, glucose, and BUN. Calculated Serum Osmolality is intended for use in: Adults.
How to Use the Calculated Serum Osmolality Calculator
- Enter Sodium in mEq/L.
- Enter Glucose in mg/dL.
- Enter BUN (blood urea nitrogen) in mg/dL.
- Click Calculate to see your result and interpretation.
Formula & Version
This calculator uses formula version 1.0, last reviewed September 2026.
Clinical Considerations & Limitations
- Does not account for unmeasured osmoles (e.g. ethanol, methanol, ethylene glycol, mannitol) — see the Osmolar Gap calculator to screen for these.
References
- Standard calculated-osmolality formula: 2×Na + Glucose/18 + BUN/2.8
Frequently Asked Questions
What is Calculated Serum Osmolality?
Estimated serum osmolality from sodium, glucose, and BUN.
Who is Calculated Serum Osmolality intended for?
Adults. Always confirm applicability to your specific patient before use.
What are the limitations of Calculated Serum Osmolality?
Does not account for unmeasured osmoles (e.g. ethanol, methanol, ethylene glycol, mannitol) — see the Osmolar Gap calculator to screen for these.
What formula or reference does Calculated Serum Osmolality use?
Standard calculated-osmolality formula: 2×Na + Glucose/18 + BUN/2.8
Is Calculated Serum Osmolality a diagnosis?
No. Calculated Serum Osmolality produces a score or estimate to support clinical decision-making — it is not a diagnosis and should be interpreted alongside full clinical judgement.
