Normal Range for Urine Creatinine

The normal range for urine creatinine is 9.46-19.01 mmol/day (1070-2150 mg/day) in men and 6.75-10.61 mmol/day (764-1200 mg/day) in women. 1

Sex-Specific Reference Ranges

Urine creatinine concentrations show significant differences between men and women, with men typically having higher values due to greater muscle mass 1, 2
Men: 9.46-19.01 mmol/day (1070-2150 mg/day) 1
Women: 6.75-10.61 mmol/day (764-1200 mg/day) 1

Muscle mass directly correlates with creatinine production and excretion 3, 2
Age affects creatinine excretion, with lower values typically seen in older adults due to decreased muscle mass 4, 2
Race/ethnicity influences creatinine levels, with higher values often seen in Black individuals 5, 2
Body mass index and fat-free mass are significant predictors of urinary creatinine concentration 2
Diet, particularly protein intake, can affect creatinine production 5
Hydration status impacts urine concentration and therefore creatinine concentration 6
Time of day when urine is collected makes a small but statistically significant difference in creatinine concentrations 2

Urine creatinine is primarily used to standardize other urinary measurements rather than as a standalone diagnostic parameter 3, 5
It serves as the denominator in protein-to-creatinine and albumin-to-creatinine ratios 4, 3
Normal protein-to-creatinine ratio is <200 mg/g 4, 3
Normal albumin-to-creatinine ratio is ≤30 mg/g creatinine 4, 3
Ratios <100 mg protein/g creatinine in untimed urines indicate normal kidney function 7
Ratios >2000 mg protein/g creatinine suggest nephrotic syndrome 7

Spot urine samples are generally preferred over 24-hour collections for convenience and accuracy 4, 3
First-morning spot collections are best for children and adolescents to avoid confounding effects of orthostatic proteinuria 4
Patients should refrain from vigorous exercise for 24 hours before sample collection 4, 3
Urine samples should be refrigerated for assay on the same or next day 4, 3
One freeze is acceptable if necessary, but repeated freeze-thaw cycles should be avoided 4, 3

Urine concentration (specific gravity) affects the accuracy of creatinine-based ratios 6
For dilute urine (specific gravity ≤1.005), protein/creatinine ratios may overestimate actual protein excretion, especially when urine creatinine is ≤38.8 mg/dL 6
For concentrated urine (specific gravity ≥1.015), protein/creatinine ratios may underestimate actual protein excretion, especially when urine creatinine is ≥61.5 mg/dL 6
When using urine creatinine for standardization, compare results with reference ranges from similar demographic groups (e.g., children with children, adults with adults) 2

Timed urine collections for creatinine clearance have largely been replaced by estimated GFR calculations using serum creatinine 4, 3
When using spot urine samples for protein or albumin assessment, the ratio to creatinine provides more reliable results than concentration alone 4, 3
For research and epidemiologic studies, multivariate analysis should include analyte concentration (unadjusted for creatinine) with urinary creatinine added as a separate independent variable 2