Urine Analysis Biomarker
Collection Type: Urine
Related System: Urine Analysis
Specific gravity (SG) of urine measures how concentrated or dilute urine is by comparing its density to pure water. It reflects the kidney’s ability to concentrate solutes (electrolytes, urea, glucose, proteins) and helps assess hydration status and renal tubular function. Abnormal SG can point to dehydration, overhydration, diabetes insipidus, syndrome of inappropriate ADH (SIADH), acute or chronic kidney disease, or significant glycosuria/proteinuria. Symptoms prompting the test include excessive thirst, very high or low urine output, dark or foamy urine, dizziness, edema, or unexplained fatigue. Newborns and infants normally have lower SG; older adults often show reduced concentrating ability. Pregnancy, sex, body size and recent fluid/food/medication intake can also alter values.
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Symptom Checker1.005-1.030 (unitless)
Q: What do you mean by specific gravity?
A: Specific gravity is the ratio of a substance’s density to the density of a reference substance (for liquids, usually water). It’s a unitless number indicating how concentrated a solution is—higher values mean more dissolved solids. Clinically, urine specific gravity (roughly 1.005–1.030) helps assess hydration and kidney concentrating ability; it’s measured with a refractometer or dipstick.
Q: What is specific gravity in a urine test?
A: Urine specific gravity is a lab measure comparing urine density to water, indicating how concentrated urine is and how well kidneys concentrate or dilute it. Normal adult range is about 1.005–1.030. High values suggest dehydration, reduced kidney perfusion or presence of glucose/protein; low values indicate overhydration, impaired renal concentrating ability, or diuretic use. It helps assess hydration and kidney function.
Q: What is specific gravity in a battery?
A: Specific gravity in a battery is the density of the electrolyte (sulfuric acid solution) relative to water. It indicates state of charge and acid concentration: a fully charged lead‑acid cell is typically around 1.265 (approx.) and a discharged cell about 1.120. Measured with a hydrometer, readings should be temperature‑corrected and can reveal sulfation, low charge, or failing cells.
Q: Why is it called specific gravity?
A: Specific gravity names the property because it expresses a substance’s density relative to a specific reference (usually water). “Specific” denotes comparison to that chosen standard; “gravity” reflects historical measurement by weight under gravity it compares the weight (force due to gravity) of equal volumes. The term thus captures a dimensionless ratio of how heavy something is compared with the reference.
Q: What is the SG of water?
A: Specific gravity (SG) is the ratio of a substance's density to that of pure water. By definition, pure water has an SG of 1.000 at 4°C; at common laboratory/room temperature (20–25°C) it’s slightly less (≈0.998–0.999). SG depends on temperature and dissolved substances, so measurements should specify temperature or use temperature‑corrected tables for accurate comparison.
Q: What is the principle of specific gravity?
A: Specific gravity is the ratio of a substance’s density to that of a reference (usually pure water at 4°C). It’s a dimensionless measure indicating how concentrated or dense a fluid is compared with water. Clinically, urine specific gravity assesses hydration and renal concentrating ability. Measurement methods include hydrometers or refractometers; temperature and solute composition can affect results.