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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 1.020 to 1.028.

Note: Normal value ranges may vary slightly among different laboratories. 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
  • Low blood sodium level
  • 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

Bazari H. Approach to the patient with renal disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 115.


Review Date: 8/7/2009
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.
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