Normal Creatinine Clearance
Normal creatinine clearance is approximately 90-120 mL/min/1.73 m² in young adults, though this value decreases significantly with age and varies by sex, body composition, and ethnicity. 1
Reference Range by Demographics
Young adults typically demonstrate creatinine clearance of 90-120 mL/min/1.73 m², which represents the standard reference range for normal kidney function 1
Age-related decline occurs even in healthy individuals: A 30-year-old male athlete may maintain a creatinine clearance of 110 mL/min, while a 75-year-old woman with identical serum creatinine may have only 40 mL/min 2, 1
Women have approximately 15% lower creatinine clearance than men of similar age and body composition 1
Ethnic variations exist: Black individuals have approximately 32.5% muscle mass versus 28.7% in white subjects of identical weight, resulting in higher baseline serum creatinine levels but not necessarily different actual clearance rates 2, 1
Clinical Measurement Considerations
Serum creatinine alone is unreliable for assessing renal function and should never be used as a standalone marker, as recommended by the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines 1
Measured 4-hour creatinine clearance correlates well with gold-standard inulin clearance (r = 0.92), though it tends to overestimate true GFR by approximately 15% in the range of 30-209 mL/min due to tubular secretion of creatinine 3
The Cockcroft-Gault formula provides superior estimates compared to serum creatinine alone for bedside assessment, with approximately 83% of estimates falling within 30% of measured GFR 3, 4
Critical Pitfalls to Avoid
Normal serum creatinine does not equal normal renal function, particularly in elderly patients, women, or those with reduced muscle mass 2, 1
In one study, 54.5% of patients with severe renal failure by Cockcroft-Gault calculation had serum creatinine values in the normal laboratory range 2
Estimated creatinine clearance should always be calculated using validated formulas (Cockcroft-Gault or MDRD) that incorporate age, weight, and sex rather than relying on serum creatinine values alone 1
Polytrauma patients may demonstrate augmented renal clearance (>120 mL/min/1.73 m²) despite normal serum creatinine, requiring measurement rather than estimation for accurate drug dosing 5