Urine osmolality is a measure of urine concentration, in which large values indicate concentrated urine and small values indicate diluted urine. It tells the ability of the kidney to maintain both tonicity and water balance of the extracellular fluid can be evaluated by measuring the osmolality of the urine either routinely or under artificial conditions.
More information concerning the state of renal water handling or abnormalities of urine dilution or concentration can be obtained if urinary osmolality is compared to serum (blood) osmolality and if urine electrolyte studies are performed.
Why do doctors have to check urine osmolality?
Your doctor may order this test if he or she wants to check your body’s water balance and assess your kidney function or if you are experiencing the following conditions:
- abnormal blood sodium level (high or low)
- complicated urinary tract infection
- excessive urination
This test also measures the amount of several compounds in your urine. The compounds that are typically present are: chloride, glucose, potassium, sodium, and urea.
Normally, in healthy individuals with restricted fluid intake, urine osmolality should be greater than 800mOsm/kg, while a 24-hour urine osmolality should average between 500 and 800 mOsm/kg and a random urine osmolality should be 50 to 1400 mOsm/kg .
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