CPT: 83930
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Special Instructions

State patient's age on the request form.

Expected Turnaround Time

1 - 3 days

Related Documents

Specimen Requirements


Serum or plasma


2 mL

Minimum Volume

0.2 mL (Note: This volume does not allow for repeat testing.)


Red-top tube, gel-barrier tube, or green-top (heparin) tube


Pediatric: Blood drawn from heelstick for capillary. Separate serum or plasma from cells as soon as possible after clot formation. Transfer specimen to a plastic transport tube.

Storage Instructions


Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Hemolysis; EDTA plasma submitted

Test Details


Evaluate electrolyte and water balance, hyperosmolar status, and hydration status; evaluate dehydration, acid-base balance; evaluate seizures; clue to alcoholism, methanol toxicity, ethylene glycol ingestion; evaluate antidiuretic hormone function, liver disease, hyperosmolar coma, evaluate hypernatremia. Osmolarity measures the concentration of particles in solution.


Freezing point depression

Reference Interval

Neonatal: may be as low as 266 mOsm/kg; 0 to 60 years: 275−295 mOsm/kg; 61 years and older: 280−301 mOsm/kg

Additional Information

High serum osmolality can result from hypernatremia, dehydration, hyperglycemia, mannitol therapy, azotemia, ingestion of ethanol, methanol, ethylene glycol. Thus, osmolality has a role in toxicology and in coma evaluation. Elevated serum osmolality with normal sodium suggests possible hyperglycemia, uremia, or alcoholism.1

Low serum osmolality may be secondary to overhydration, hyponatremia, syndrome of inappropriate antidiuretic hormone secretion (SIADH) with carcinoma of lung and other entities.


1. Weisberg HF. Unraveling the laboratory model of a syndrome: The osmolality model. In: Young DS, Hicks J, Nipper H, et al, eds. Clinician and Chemist. The Relationship of the Laboratory to the Physician. Washington, DC: American Association of Clinical Chemistry;1979:200-243.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
002071 Osmolality 2692-2 002071 Osmolality mOsmol/kg 2692-2

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