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Laboratory Medicine

Test Directory / Osmolality


Brown clotted serum, gel barrier

Common AbbreviationsOSM
Tube typeBrown clotted serum, gel barrier
Clinical IndicationDetermination of serum and urine osmolality can be useful in the assessment of electrolyte and acid-base disorders. Comparison of serum and urine osmolalities can determine the status of renal water regulation in settings of severe electrolyte disturbances as might occur in diabetes insipidus or the syndrome of inappropriate anti-diuretic hormone. Osmolality may also be performed as part of a water deprivation test (used in the diagnosis of diabetes insipidus) or where there is suspicion of ingestion of an osmotically active substance such as ethanol, methanol or ethylene glycol.
Specimen TypeBlood
Sample typeSerum
Minimum Volume0.5mL If requesting more than 10 tests please send an additional brown clotted serum sample.
Special PrecautionsNo special requirements
StabilitySerum: 4 days at room temperature and 8 days at 4°C Whole blood: 12 hours at room temperature and ? 14 days at 4°C
Turnaround TimeInpatient: 24 hours Outpatient/ GP: 24 hours
LaboratoryYork and Scarborough
Reference Interval275-295 mOsm/kg
LimitationsAdditives, such as anticoagulants found in some collection containers, may contribute significantly to the measured osmolality and should NOT be used.
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