Normal Serum Creatinine Range in Adults
Normal serum creatinine ranges from approximately 0.55–1.02 mg/dL (49–90 µmol/L) in adult women and 0.73–1.18 mg/dL (65–104 µmol/L) in adult men when measured by enzymatic methods. 1
Sex-Specific Reference Ranges
Adult Women
- 0.55–1.02 mg/dL (49–90 µmol/L) using enzymatic assays 1
- 0.48–0.93 mg/dL using IDMS-traceable enzymatic methods in Caucasian populations 1
- Mean value: 0.70 mg/dL in women aged 20–70 years 1
Adult Men
- 0.73–1.18 mg/dL (65–104 µmol/L) using enzymatic assays 1
- 0.63–1.16 mg/dL using IDMS-traceable enzymatic methods in Caucasian populations 1
- Mean value: 0.90 mg/dL in men aged 20–70 years 1
Age-Related Variations
The creatinine-age relationship is not linear and requires careful interpretation:
- Birth to 14 years: Serum creatinine increases equally in boys and girls 1
- 14 to 20 years: Boys show a much steeper increase than girls, reflecting greater muscle mass development 1
- 20 to 70 years: Values remain relatively constant at the ranges listed above 1
- Above 70 years: Creatinine begins to slowly increase again despite declining GFR, due to age-related muscle mass loss 1
Ethnic Variations in Population Studies
Mean creatinine levels vary by ethnicity, though the clinical significance remains unclear:
- Non-Hispanic Black adults: Highest mean values (women 1.01 mg/dL, men 1.25 mg/dL) 2
- Non-Hispanic White adults: Intermediate values (women 0.97 mg/dL, men 1.16 mg/dL) 2
- Mexican-American adults: Lowest values (women 0.86 mg/dL, men 1.07 mg/dL) 2
Critical Clinical Caveats
Never Use Serum Creatinine Alone
Serum creatinine concentration should never be used as the sole means to assess kidney function (Level A recommendation). 3
- A "normal" creatinine of 1.2 mg/dL can represent a creatinine clearance of 110 mL/min in a young adult but only 40 mL/min in an elderly patient 3, 4
- GFR must decline to approximately half the normal level before serum creatinine rises above the upper limit of normal 4
- Among elderly patients with calculated GFR ≤50 mL/min, 40% had serum creatinine levels within the normal laboratory range 4
Factors That Distort the Creatinine-GFR Relationship
High muscle mass (bodybuilders, athletes) artificially elevates serum creatinine independent of kidney function 4
Low muscle mass (elderly, sarcopenia, chronic illness, malnutrition) falsely lowers serum creatinine, masking significant renal impairment 4
Other confounding conditions:
- Skeletal muscle diseases (muscular dystrophy, myopathies, ALS) 4
- Paraplegia or quadriplegia 4
- Severe malnutrition or obesity 4
- Vegetarian diet (reduces dietary creatine intake) 4
- Creatine supplementation (increases creatinine production) 4
Mandatory Next Step: Calculate Estimated GFR
Always calculate estimated GFR using validated equations:
- For CKD diagnosis/staging: Use the 2021 CKD-EPI equation without race or MDRD equation 5
- For medication dosing: Use the Cockcroft-Gault formula 5
- Clinical laboratories should automatically report eGFR whenever serum creatinine is measured 5
Laboratory Method Considerations
Enzymatic methods are preferred over the Jaffe method because Jaffe overestimates serum creatinine by 5–15% 5
IDMS-traceable calibration is mandatory for accurate creatinine measurement, with coefficient of variation <2.3% and bias <3.7% 5
When to Use Alternative Assessment Methods
Consider cystatin C-based eGFR or direct GFR measurement in: