Calculated Serum Osmolality
Estimates serum osmolality from basic metabolic panel to evaluate osmolar gap and dysnatremia
- Highest activation tier
- Recommended
- How it is scored
- Scored in code; a detected disagreeing draft value is flagged for correction
- Scoring type
- formula
- Care settings
- Any setting
When it activates
Scribeable activates a calculator from the encounter. The Calculated Serum Osmolality can activate when the transcript or pasted chart context documents any of these:
- Hyponatremia workup
- DKA osmolality assessment
- Hyperosmolar hyperglycemic state (HHS)
- Toxic alcohol ingestion evaluation
- Osmolar gap calculation
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: E11.0, E13.1, E87.0, E87.1, T51.
Inputs the note needs
3 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; at this calculator’s tier a missing input is never requested, and a missing required input keeps the score out of the draft.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| Serum sodium in mEq/L | lab | mEq/L | |
| Serum glucose in mg/dL | lab | mg/dL | |
| Blood urea nitrogen in mg/dL | lab | mg/dL |
Scoring
Calculated Osm = 2×Na + glucose/18 + BUN/2.8
Osm = 2×Serum sodium in mEq/L + Serum glucose in mg/dL/18 + Blood urea nitrogen in mg/dL/2.8
Interpretation
Normal: 275–295 mOsm/kg. Osmolar gap (measured − calculated) >10: consider toxic alcohols (methanol, ethylene glycol), isopropanol, or unmeasured osmoles. DKA/HHS often >320. <275 with hyponatremia: hypotonic hyponatremia workup.
Evidence
Sources carried in Scribeable's citation registry for this calculator; guideline version: Standard formula.
- Fazekas AS et al. Evaluation of 36 formulas for calculating plasma osmolalitySerum Osmolality Formula · 2013 · link last verified 2026-03-28
How Scribeable handles it in the note
When an encounter activates the Calculated Serum Osmolality (its highest tier is recommended), Scribeable does not ask you for missing inputs. The score is computed in code from whatever inputs resolve from the transcript, the pasted chart context or charted labs; a computed value is written into the draft only when every required input already resolves.
The score is computed in code from the resolved inputs, not recalled by the language model. If the draft states a Calculated Serum Osmolality value that disagrees with the computed one, the disagreement is flagged to the second drafting pass, which is instructed to correct the score and its interpretation before you see the note.
Classified as a deterministic formula: a spare suggestion is easy to ignore, so activation is permissive.
See it activate on your own encounter
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