Osmolality, Urine


Urine osmolality, like specific gravity, is a measurement of the concentration of urine. Urine osmolality reflects the total number of osmotically active particles in the urine, without regard to the size or weight of the particles. See Also Osmolality, Serum


Increased in syndrome of inappropriate ADH secretion. Decreased in diabetes insipidus and primary polydipsia. Simultaneous determination of urine and serum osmolalities facilitates interpretation of results. High urinary/plasma ratio is seen in concentrated urine. Patients with impaired renal function may not be able to concentrate urine. As a result, the urine osmolality will resemble that of plasma.

Sample Type, Quantity & Conditions

5 ml Urine Stability: 7 Days at 2-8 °C

Special Precautions

Needed Tests for calculation: Urea, Glucose and Sodium. Calculated

Normal Range

300-900 mOsm/Kg

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