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Osmolality

CPT: 83930
Updated on 09/22/2020
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Special Instructions

State patient's age on the request form.


Expected Turnaround Time

1 - 3 days


Related Documents


Specimen Requirements


Specimen

Serum or plasma


Volume

2 mL


Minimum Volume

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


Container

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


Collection

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

Refrigerate


Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3


Causes for Rejection

Hemolysis; EDTA plasma submitted

Hemolysis

Hemolysis; EDTA plasma submitted


Test Details


Use

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.


Methodology

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.


Footnotes

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.

LOINC® Map

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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