urine osmolality test

A urine osmolality test is a measure of the concentration of dissolved minerals (like sodium or salt) and wastes (like BUN) in a person's urine relative to water content.

 

Higher mineral content and lower amounts of water lead to a high osmolality.

 

Osmolality also provides information about the body's ability to excrete certain materials (low excretion means kidney damage) and balance fluids like water (when someone drinks a lot of water, there is more in the urine and therefore a lower osmolality).

 

A urine osmolality test is done when either a water balance or kidney problem is suspected.

 

A urine sample—usually either a first morning sample or a sample at a time determined in advance by the healthcare provider-- is required for this test.

 

To collect a specimen, a person should:

 

The container should be covered and brought to the healthcare provider or lab for testing. Sometimes the test itself will be supervised in the hospital.

 

Since test preparations vary, a person should ask a healthcare provider for specific instructions. First morning samples often are collected after a fast (no food or water) of 8-12 hours or so.

Urine osmolality is dependent on 3 things: kidney functionwater intake or lack thereofthe level of hormones released from the pituitary gland that help reabsorb water in the kidney (called Antidiuretic Hormone or ADH).