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Urine specific gravity

Definition:

Urine specific gravity is a laboratory test that measures the concentration of all chemical particles in the urine.

See also:



Alternative Names:

Urine density



How the test is performed:

The test requires a clean-catch urine sample. For information on how to collect this urine sample, see: Clean-catch urine culture



How to prepare for the test:

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. Drugs that can increase specific gravity measurements include dextran and sucrose. Receiving intravenous dye (contrast medium) for an x-ray exam up to 3 days before the test can also interfere with results.

Eat a normal, balanced diet for several days before the test.



How the test will feel:

The test involves only normal urination, and there is no discomfort.



Why the test is performed:

This test helps evaluate your body's water balance and urine concentration.



Normal Values:

Normal values are between 1.000 to 1.030.

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.



What abnormal results mean:

Increased urine specific gravity may be due to:

  • Addison's disease (rare)
  • Dehydration
  • Diarrhea that causes dehydration
  • Glucosuria
  • Heart failure (related to decreased blood flow to the kidneys)
  • Renal arterial stenosis
  • Shock
  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH )

Decreased urine specific gravity may be due to:

Additional conditions under which the test may be performed:

  • Complicated UTI (pyelonephritis)
  • High blood sodium level (hypernatremia)
  • Low blood sodium level (hyponatremia)
  • Excessive urination


Special considerations:

Osmolality is a more specific test for urine concentration. However, the specific gravity measurement is easier and more convenient and usually part of a routine urinalysis. It frequently makes the osmolality measurement unnecessary.



References:

Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 116.




Review Date: 8/21/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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