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.
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:
Kidney disease or disorder
Eaten a toxic substance
You may also need this test if you have:
Ongoing (chronic) diarrhea
Severe, prolonged vomiting
High or low blood sodium
Fluid loss (dehydration)
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.
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results 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:
Glomerulonephritis, a type of kidney disease
Excessive water intake
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.
This test poses no known risks.
A high-protein diet could increase your osmolality levels. Drinking large amounts of water could lower them.
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.