Specific Gravity, Urine

Diagnostic Use

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 (e.g., sodium, chloride, potassium), they disproportionately affect SG. In these cases, urine osmolality is a better measure of urine concentration.

Department

Specialist Biochemistry

Delphic Registration Code

GUC

Laboratory Handling

Test Adds

Refrigerated (preferred) 7 days, frozen 7 days

Synonyms

SG

Turnaround Time

7 days

Test Code

3090

Specimen Type

• Urine

Specimen Requirements

Tube/Container Type:

Preferred

• Pottle

Preferred Sample Volume (ml)

2.0

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Pottle

Preferred Sample Volume (ml)

2.0

Aliquot Instructions

Sample Type

• Urine

Minimum Volume (ml)

2.0

Transport to Lab

Chilled (2 - 8 degrees Celsius)

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 diarrhoea.

Reference Intervals

1.002 – 1.030

Test Method

Refractometer

Non-Funded Test Cost

$18.95 (Exclusive of GST)

Billing Code

3796

Patients administered radio opaque dyes give falsely high results.

Contact Information

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