Does this test have other names?
What is this test?
This test measures the concentration (osmolality) of particles in your urine. It finds
out if your electrolyte balance is normal and if your kidneys are working as they
should. Electrolytes are mineral salts that help move nutrients into your cells and
move waste products out of your cells.
Why do I need this test?
You may need this test if your healthcare provider needs to look at the concentration
of your urine, as well as at your fluid and electrolyte balance. This may be needed
if your provider thinks you may have:
You may also need this test if you have:
What other tests might I have along with this test?
You may also need some of these tests:
Blood urea nitrogen, or BUN
Blood glucose test to rule out diabetes mellitus
Blood osmolality test
Blood calcium and albumin
You may need some of these tests if the concentration of sodium in your blood is too
high or too low.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
Results of this test are given in millimoles per kilogram (mmol/kg). A range of 50
to 1,200 mmol/kg is considered normal.
If your results are higher than normal, you may have one of these conditions:
Too much sugar in your urine (glycosuria)
Heart failure, if you also have low urine sodium
Liver cirrhosis, if you also have low urine sodium
Results that are lower than normal could mean you have:
How is this test done?
This test is done with a urine sample. It may be a random urine sample or one that
is collected over a 24-hour period.
Does this test pose any risks?
This test poses no known risks.
What might affect my test results?
A high-protein diet could increase your osmolality levels. Drinking large amounts
of water could lower them.
How do I get ready for this test?
You don't need to prepare for this test. Be sure your healthcare provider knows about
all medicines, herbs, vitamins, and supplements you are taking. This includes medicines
that don't need a prescription and any illegal drugs you may use.