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HelpTest ID SGUR Specific Gravity, Random, Urine
Ordering Guidance
Urine with contrast dye, glucose, or excessive protein should not be evaluated with this test. In these cases, urine osmolality is a better measure of urine concentration. Order UOSMU / Osmolality, Random, Urine.
Specimen Required
Container/Tube: Plastic urine container
Specimen Volume: 20 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
Useful For
As a partial assessment of the kidney's ability to concentrate urine
Method Name
Refractometer
Reporting Name
Specific Gravity, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 7 days | |
| Frozen | 7 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Specific gravity (SG), the ratio of the mass of a solution compared to the mass of an equal volume of water, is an estimate of the concentration of substances dissolved in the solution.
Urine SG can be used to assess the kidney's ability to concentrate or dilute urine. However, because protein, glucose, and contrast dye have molecular masses that are relatively large compared to other major components of urine (eg, sodium, chloride, potassium), they disproportionately affect SG. In these cases, urine osmolality is a better measure of urine concentration
Reference Values
1.002-1.030
Interpretation
Low specific gravity (SG) (1.001-1.003) may indicate the presence of diabetes insipidus, a disease caused by impaired functioning of antidiuretic hormone (ADH). Low SG also can occur in patients with glomerulonephritis, pyelonephritis, and other renal abnormalities. In these cases, the kidney has lost its ability to concentrate due to tubular damage.
High SG may occur in patients with adrenal insufficiency, hepatic disease, congestive heart failure, or in patients experiencing excessive water loss due to sweating, fever, vomiting, or diarrhea.
Cautions
No significant cautionary statements
Clinical Reference
1. Schumann GB, Schweitzer SC: Examination of urine. In: Kaplan LA, Pesce AJ, eds. Clinical Chemistry, Theory, Analysis and Correlation. 3rd ed. Mosby-Year Book Inc; 1996:1118-1119
2. Free HM, ed: Modern Urine Chemistry (Manual). 8th ed. Bayer Corp; 1996:36-37
3. Perrier ET, Bottin JH, Vecchio M, Lemetais G: Criterion values for urine-specific gravity and urine color representing adequate water intake in healthy adults. Eur J Clin Nutr. 2017 Feb;71:561-563
Method Description
The refractive index of a material, which is its light-bending power as compared to air, is a physical constant, which varies directly with the chemical composition of a substance. This is accomplished by viewing a drop of solution through a lens-prism system of the total solids meter (refractometer). The refractometer measures total solids in urine to an accuracy of 0.1 g/100 mL and since it requires about 0.25 g/100 mL in total solids to change the specific gravity by about 0.001 units, optical urinometry proves excellent for clinical measurement of specific gravity. Refractometers are temperature compensated and will read standards correctly only at temperatures between 20° C and 30° C.(Minton DM, O’Neal EK, Torres-McGehee TM: Agreement of urine specific gravity measurements between manual and digital refractometers. J Athl Train. 2015;50[1]:59-64)
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.NY State Approved
YesForms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Day(s) Performed
Monday through Sunday