Overview & Description
A urine osmolality test measures the osmolality, or concentration of particles, in a person's urine.
It provides information about the body's ability to balance fluids and other substances.
Who is a candidate for the test?
A urine osmolality test is done when fluid balance or kidney problems are suspected.
How is the test performed?
A mid-stream, or clean-catch, urine
sample is required for this test.
First, the entire area around the urethra should be
washed off to prevent contamination of the sample. Then, a person should:
start urinating into the toilet
move the container to catch a sample of urine
take away the container and finish urinating into the toilet
The container should be covered and brought to the healthcare provider or lab for testing.
Preparation & Expectations
What is involved in preparation for the test?
Since test
preparations vary, a person should ask a healthcare provider for specific instructions.
Results and Values
What do the test results mean?
Normally, urine has an osmolality of 50
to 1,400 mOsm/kg H20 (milliosmoles per kilogram of water).
Abnormally high osmolality may be a sign of:
Addison's disease, which is caused by a deficiency of hormones produced in the adenal glands
irregularities in the secretion of antidiuretic hormone, or ADH. ADH helps the
kidneys put water back into the bloodstream.
congestive heart failure, or a weakened heart that fails to pump enough blood to body cells
Abnormally low osmolality may be a sign of:
aldosteronism, a condition in which a person has too much of the hormone
aldosterone, which helps the body break down and use sodium, chloride, and potassium
diabetes insipidus, a disease which causes increased thirst and urination
excessive fluid intake, which occurs when a person drinks too much fluid
kidney damage or disease
pyelonephritis, a kidney inflammation usually caused by an infection
Homepage 
Health
Topics 
Diabetes 
