Test Overview
Test Methodology

Advanced Instruments Osmometer -freezing-point depression

Test Usage

Performed at authorized locations by point of care operators. Serum and Urine osmolality are included.
Hyper osmolality in serum is most often associated with diabetes mellitus, and uremia. Abnormally low ratios occur in disease states such as; lymphomas, cancer, liver failure, shock, acute infections, and myocardial infarctions. In special cases of acute toxicity due to overdose of drugs, findings of normal serum sodium and high serum osmolality may be considered as an indication for dialysis. In dehydration, where water loss exceeds salt loss, the osmolality and the serum sodium increase, but the ratio stays normal. Examples are prolonged diarrhea and peritonitis or intestinal obstruction in which fluid has been sequestered outside the vascular system.

Reference Range *

Reference ranges are available in the Osmolality test procedure located on the POC website: https://www.pathology.med.umich.edu/point-of-care.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

No significant interference due to hemolysis, icterus, or lipemia. A comment should be entered with the results if grossly hemolyzed specimens are tested.

Test Details
Analytic Time

2-3 minutes

Soft Order Code
MiChart Code
Osmolality, Point of Care
Point of Care
Point of Care
Specimen Requirements
Collection Instructions

Collect blood in SST or sodium, lithium heparin for serum osmolality measurement. Collect urine in plastic urine cup.

Special Handling

Serum (SST or red top tubes) must be spun at 4000 rpm for 12 minutes before being processed.

Normal Volume
3 mL
Minimum Volume
50 µL
Rejection Criteria
Samples collected in sodium citrate (blue top), EDTA ( lavender top), potassium oxalate or sodium fluoride (gray tops) are unacceptable.
Additional Information

For more test specific information, please refer to the test procedure found on the Michigan Medicine POC website: https://www.pathology.med.umich.edu/point-of-care

CPT Code
serum osmolality(2692-2), urine osmolality(2695-5)