Urine Specific Gravity
Kidney Function marker
Urine Specific Gravity
A measure of how concentrated the urine is, expressed as the ratio of urine density to water (roughly 1.000 to 1.035). It reflects hydration status and the kidney's ability to concentrate urine, and it provides essential context for interpreting other spot-urine readings.
PED Notes
Specific gravity is largely a hydration readout, which makes it very relevant to bodybuilding practices. Diuretic use and water manipulation during contest prep, plus stimulant fat-burners and simple under-drinking, concentrate the urine and push specific gravity high. That concentration is not just a hydration marker: it directly distorts other spot-urine tests. A dipstick protein, glucose, or blood reading looks falsely elevated in highly concentrated urine and falsely reassuring in very dilute urine, so specific gravity should be read first when interpreting a urinalysis. Persistently dilute urine (low specific gravity) despite fluid restriction can point to impaired concentrating ability. Aggressive dehydration for stage or weigh-ins also raises kidney-stone risk. Values are lab and refractometer dependent.
When high
When specific gravity is high (concentrated urine):
- Usually means dehydration: from diuretics, water cutting, stimulant fat-burners, hot-weather training, or simply not drinking enough.
- Rehydrate and re-test; interpret any raised dipstick protein, glucose, or blood cautiously, because concentrated urine exaggerates them.
- Chronic concentration (common in dieting/cutting athletes) raises the risk of uric acid and calcium stones: increase fluid to produce pale urine and 2.5-3L output per day.
When low
When specific gravity is low (dilute urine):
- Often simply reflects a high fluid intake around the time of collection.
- Persistently low specific gravity despite fluid restriction can indicate reduced renal concentrating ability or excessive water intake; if unexplained, investigate for causes of impaired concentration.
- In dilute urine, a "negative" dipstick for protein or blood is less reassuring, because dilution can mask a genuine finding: repeat on a first-morning sample if suspicion remains.
Interpretation note:
- Always read specific gravity alongside the rest of the urinalysis. It calibrates every other spot-urine result: concentrated urine inflates them, dilute urine deflates them. A first-morning sample gives the most consistent assessment of concentrating ability.
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range