Your Hydration Gauge
Specific gravity measures how concentrated your urine is—essentially how hydrated you are. Pure water has a specific gravity of 1.000. The more stuff dissolved in your urine (waste products, electrolytes), the higher the specific gravity. Low SG = dilute (well-hydrated or kidney can't concentrate). High SG = concentrated (dehydrated or SIADH).
What is Urine Specific Gravity?
Specific gravity measures urine density relative to water. Refractometer is most accurate. Dipstick estimates based on ionic strength. Normal: 1.005-1.030. Fixed at 1.010 = isosthenuria (kidneys can't dilute or concentrate—suggests renal failure).
↑ What High Urine Specific Gravity Means
Concentrated urine. Usually dehydration. Also: SIADH, contrast dye, glucose in urine (diabetes), or protein in urine.
Common symptoms:
Dark urine · Thirst · Headache · Fatigue (dehydration)
↓ What Low Urine Specific Gravity Means
Dilute urine. Could be excellent hydration, diabetes insipidus (kidneys can't concentrate urine), or excessive water intake. Fixed at 1.010 (isosthenuria) = kidney failure.
Common symptoms:
Frequent urination with large volumes (if DI) · Excessive thirst (if DI)
Why It Matters
When normal:
Quick hydration assessment
Validates urine sample (very dilute may give false negative drug screen)
Fixed SG suggests kidney failure
Helps interpret other urine findings (concentrated urine can cause false positives)
Risks if abnormal:
Very high: dehydration, kidney stone risk
Very low persistently: diabetes insipidus or excessive water intake
Fixed at 1.010: renal failure
What Can Cause Abnormal Levels?
Dehydration (high)
50% likelyMost common cause of concentrated urine.
Overhydration / Excessive Water Intake (low)
30% likelyMost common cause of dilute urine.
Diabetes Insipidus (persistently low)
Central (no ADH) or nephrogenic (kidneys don't respond to ADH). Urine stays dilute despite dehydration.
SIADH (high)
Excess ADH causes concentrated urine despite low serum sodium.
Chronic Kidney Disease (fixed at 1.010)
Kidneys lose ability to concentrate or dilute. SG stuck near plasma osmolality.
What You Can Do
If high: drink more water
Impact: Simple dehydration is the most common cause \u00B7 Timeline: Immediate
If low: usually just well-hydrated
Impact: Not concerning unless persistent despite fluid restriction \u00B7 Timeline: N/A
If lifestyle changes aren't enough:
If fixed at 1.010 with rising creatinine: evaluate for CKD
Impact: Isosthenuria indicates significant kidney dysfunction \u00B7 Timeline: As needed
Recommended retest: Not routinely monitored; used for clinical context
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