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Urine specific gravity
Alternative namesUrine density; Urine s.g.
DefinitionUrine specific gravity measures the concentration of particles in the urine (see also urine concentration test ).
How the test is performed
Child or adult:
This procedure may take a couple of attempts -- lively infants can displace the bag, causing the specimen to be absorbed by the diaper. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.
How to prepare for the testThe health care provider may advise you to withhold drugs that can affect the test (see "special considerations").
Eat a normal, balanced diet for several days before the test.
If the collection is being taken from an infant, a couple of extra collection bags may be necessary.
How the test will feelThe test involves only normal urination, and there is no discomfort.
Why the test is performed
Specific gravity measures the concentration of particles in a solution (grams/ml). Osmolality is a more exact measurement of urine concentration than specific gravity because specific gravity depends on the precise nature of the molecules present in the urine.
Specific gravity also requires correction for the presence of glucose or protein. But the specific gravity measurement is easier and more convenient to test. It frequently makes the osmolality measurement unnecessary.
Normal ValuesNormal values are between 1.002 to 1.028. Normal value ranges may vary slightly among different laboratories.
What abnormal results mean
Abnormal results indicate the following:
Increased urine specific gravity may indicate:
What the risks areThere are no risks.
Special considerationsDrugs that can increase specific gravity measurements include dextran and sucrose, and radiographic contrast medium within 3 days.
Update Date: 2/11/2004Irfan A. Agha, M.D., Department of Medicine, Renal Division, St. Louis University, St. Louis, MO. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT