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Specific Gravity Test

Published: August 9, 2026Updated: August 16, 2026

Measures the relative density of a fluid sample compared with water. It is commonly used to assess how concentrated a urine sample is.

Quick summary

["Specific gravity helps show whether a fluid sample is more or less concentrated than water."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
101569-2
Short code
Spec
Synonyms
Spec
Category
urine
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

Specific gravity measures the density of a fluid sample relative to water. It is most often used with urine to help evaluate how concentrated the sample is.

Why might I need this test?

Your clinician may order this test as part of a urinalysis or to assess fluid balance, hydration, kidney function, or the presence of substances that affect urine concentration.

How is the test performed?

A laboratory instrument, often a refractometer, measures the specific gravity of the submitted fluid sample. The sample is typically urine, although the abbreviation in this result does not specify the specimen.

How do I prepare for the test?

Follow your clinician or laboratory collection instructions. For a urine collection, the container and collection time may matter, and the sample should be handled and stored as directed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Specific gravity

Frequently asked questions

Is a high specific gravity result always a problem?
No. It may be expected after dehydration, exercise, or a period of reduced fluid intake. Your clinician will interpret it alongside your symptoms and other laboratory results.
Does a low specific gravity result mean I am drinking too much water?
Not necessarily. Dilute urine can have several causes, and it may be related to medications or kidney function. Discuss an unexpected result with your clinician.
Can this test be performed on blood or other fluids?
Specific gravity can be measured for some fluids, but the abbreviation provided does not identify the specimen. The reference information and interpretation depend on the sample type and laboratory method.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy