Normal Urine Specific Gravity Range in Children
The normal urine specific gravity range for children is 1.010 to 1.025, with first-morning values typically being higher at 1.015 to 1.025. 1
Understanding Urine Specific Gravity in Children
Urine specific gravity is an important measure of the kidney's ability to concentrate or dilute urine. It reflects the ratio of the density of urine compared to water (which has a specific gravity of 1.000).
Normal Ranges by Age:
- Infants and young children: 1.010-1.025
- School-age children: 1.010-1.025
- First morning void: Should be 1.025 or higher after overnight fluid restriction 2
Clinical Significance:
- Values below 1.010 suggest dilute urine
- Values above 1.025 indicate concentrated urine
- First-morning urine specific gravity after taking no fluids for 12 hours overnight should be 1.025 or more 2
Measurement Methods
Several methods exist for measuring urine specific gravity, with varying degrees of accuracy:
- Refractometry: Highly accurate, shows good correlation with osmolality (r=0.81) 3
- Hydrometry: Also accurate, shows good correlation with osmolality (r=0.86) 3
- Reagent strips (dipsticks): Less reliable, particularly in neonates (r=0.46) 3, 4
Important Note:
Reagent strips are not reliable for precise measurement of urine specific gravity and should not be used as the sole test, especially in neonates 3, 4. When using reagent strips in newborns, values up to 1.015 reliably indicate hypotonic urine, but higher values can be misleading 4.
Clinical Applications
Diagnostic Value:
- Enuresis evaluation: In children with nocturnal enuresis, first-morning urine specific gravity is often lower than 1.015, while healthy children typically have values greater than 1.020 5
- Urinary tract infection assessment: The diagnostic performance of urinalysis for UTI varies by urine concentration. As specific gravity increases, the positive likelihood ratios for leukocyte esterase and pyuria decrease 6
- Hydration status: Helps assess fluid balance in children
Factors Affecting Urine Specific Gravity:
- Hydration status: Dehydration increases specific gravity
- Diet: High protein or salt intake can increase specific gravity
- Medications: Certain drugs can alter values
- Medical conditions: Diabetes, kidney disease, SIADH can affect readings
- Time of collection: First morning void typically has higher values
Common Pitfalls in Interpretation
Method variability: Different measurement methods yield different results; refractometry typically gives higher values than hydrometry 3
Confounding factors: Urine pH ≥6.5, glucosuria, proteinuria, and hematuria can affect readings, especially with dipstick methods 4
Age considerations: Neonates have less ability to concentrate urine, making interpretation more challenging 4
Sample timing: Random samples are less informative than first morning void specimens
For accurate clinical assessment, it's best to use refractometry or hydrometry rather than dipstick methods, and to consistently use the same method for follow-up measurements 3.