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Urine osmolality

Urine tests · also printed as Urinary osmolality, Osmolality (urine), Urine osmo, Urine osm

Typical UK adult range50 to 1200 mOsm/kg

50 to 1200 is the physiological span; there is no single typical value.

What this test measures

Urine osmolality measures how concentrated the urine is. It shows how well the kidney can concentrate or dilute urine.

Why doctors request it

Used when blood sodium is abnormal, in excessive thirst, or when checking the kidney's concentrating ability.

What commonly pushes it up

Dehydration or a concentrated overnight sample
Some medicines and hormone conditions

What commonly pushes it down

Drinking a lot of water
Some kidney conditions and some medicines as a class, for example lithium
Diabetes insipidus

Everyday reasons for a value outside the range

A first-morning sample is naturally concentrated
Fluid intake before the sample changes it completely

About the sample

Read alongside blood osmolality and sodium.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

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This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.