Collect a 24-hour urine sample for creatinine
Measure urine creatinine concentration
Measure urine volume collected over 24 hours
Measure serum creatinine concentration
Use the formula: Creatinine clearance = (Urine creatinine × Urine volume) / (Serum creatinine × Time)
Convert urine volume to mL/min if using a 24-hour collection
Use consistent units for all values
Common 24-hour formula: CrCl = (Ucr × V) / (Scr × 1440)
Adjust for body surface area if needed: CrCl normalized to 1.73 m²
For estimated creatinine clearance, use the Cockcroft-Gault formula
Cockcroft-Gault formula: CrCl = [(140 – age) × weight] / (72 × serum creatinine)
Multiply the Cockcroft-Gault result by 0.85 for females
Use creatinine in mg/dL and weight in kg for Cockcroft-Gault
Interpret the result in mL/min