Osm
Medical abbreviation · Laboratory Test
| Stands for | Osmolality |
|---|---|
| Categories | Medical |
Osm stands for Osmolality, a laboratory test abbreviation.
Concentration of dissolved particles per kilogram of water in serum or urine, measured by freezing-point depression. Serum osmolality is normally about 275 to 295 mOsm/kg and is central to the workup of hyponatremia, hyperglycemic crises and suspected toxic alcohol ingestion.
Example: Serum Osm 312 vs calculated 288: osmolal gap of 24, consistent with ethylene glycol.
Usage notes
Calculated osmolality equals twice the sodium plus glucose divided by 18 plus BUN divided by 2.8 (US units). A measured value more than about 10 above the calculated one (an osmolal gap) suggests unmeasured substances such as methanol, ethylene glycol or ethanol. Osmolality (per kilogram) is technically distinct from osmolarity (per liter), though the numbers are close in blood.
Related abbreviations
More laboratory test abbreviations
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- Na – Sodium
- NAAT – Nucleic acid amplification test
- NH3 – Ammonia
- non-HDL-C – Non-high-density lipoprotein cholesterol
- O&P – Ova and parasites
- PaCO2 – Partial pressure of arterial carbon dioxide
- PaO2 – Partial pressure of arterial oxygen
- PBS – Peripheral blood smear
- PCR – Polymerase chain reaction
- PCT – Procalcitonin
- Phos – Phosphorus (serum phosphate)
See all 135 laboratory test abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.