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Test ID: Osmolality
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Osmolality
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Useful For
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Assessment of body fluid and electrolyte balance. Aid in diagnosis of dehydration,hyponatremia/hypernatremia, kidney damage, or poisoning from toxic substances.
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Method name and description
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Freezing Point Depression Osmometry
Osmometry measures the total molar concentration of dissolved solids in any solution. The freezing point of a solution is depressed in direct relation to the amount of solute in solution.
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Clinical information
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Osmolality tests measure the amount of certain substances in blood, urine, or stool. These include glucose (sugar), urea (a waste product made in the liver), and several electrolytes, such as sodium, potassium, and chloride. Electrolytes are electrically charged minerals. They help control the amount of fluids in your body. The test can show whether you have an unhealthy balance of fluids in the body. An unhealthy fluid balance can be caused by many different conditions. These include excess salt intake, kidney disease, heart disease and some types of poisoning. The serum/plasma osmolality test measures concentration of all chemical particles found in the fluid part of blood.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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Collect blood by standard venipuncture techniques as per specimen requirements. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer.
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Storage and transport instructions
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Storage: 24 hours at room temperature
7 days at 2 – 8°C;
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic samples, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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0 to 150 years: 275-295 mOsml/kg
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
STAT: 1 hour
Routine: One working day
Specimen Retention: 4 days
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