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ID:144 Osmolality (urine)
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DescriptionA measure of urine tonicity / concentration
IndicationInvestigation of polyuria.
Additional InfoPrimary polydipsia can cause a low urine osmolality and should be considered as a cause particularly in psychiatric patients. Primary polydipsia will be associated with a dilutional hyponatraemia. With primary polydipsia urine may remain dilute even with fluid restriction but serum osmolality is often low or low to normal. A prolonged water deprivation test may be required.
Concurrent Testsna
Dietary Requirementsna

InterpretationA urine osmo >750 mOsmol/Kg excludes DI as a cause of polyuria (in classic DI serum osmolality increases >300 and urine osmolality remains <350 mOsmol/Kg). However, a low urine osmolality is NOT diagnostic of DI.

Ref. Range (Male)
Ref. Range (Female)
Ref. Range (Paed)
Ref. Range Notes

IP Acute TATRefer to Website
IP Routine TATRefer to Website
GP Acute TAT- Contact Laboratory
GP Routine TATRefer to Website
Turnround CommentOsmolality analysis will only be treated as urgent if the lab is contacted, and in such instances will have a TAT of 3hrs
Originally edited by : JHB. Last edited on 10/04/2019 14:13:20. Published By S.Bennett on 10/04/2018 14:13:20.