What is creatinine clearance?
Creatinine clearance (CrCl) estimates how well the kidneys filter the blood. It is given in mL/min.
In practice we estimate it with the Cockcroft–Gault equation. Most drug dosing tables in the BNF and SmPCs use this figure.
Cockcroft–Gault formula (µmol/L)
UK labs report creatinine in µmol/L. The formula then becomes:
CrCl (mL/min) = (140 − age) × weight (kg) × F ÷ serum creatinine (µmol/L)
F = 1.23 for men, 1.04 for women
F = 1.23 for men, 1.04 for women
If you have creatinine in mg/dL, multiply by 88.4 to convert to µmol/L first.
Worked example
A woman aged 78, weighing 62 kg, with creatinine 98 µmol/L:
(140 − 78) × 62 × 1.04 ÷ 98 = 41 mL/min
Creatinine clearance vs eGFR
| Creatinine clearance | eGFR | |
|---|---|---|
| Units | mL/min | mL/min/1.73m² |
| Uses weight | Yes | No |
| Main use | Drug dosing | Diagnosing and staging CKD |
The MHRA advises using CrCl for DOACs. This matters most in older, frail or underweight patients. In these groups eGFR can overestimate kidney function.
Which weight should I use?
- Use actual body weight for most adults.
- In obesity, actual weight may overestimate clearance.
- Ideal body weight may suit some drugs. Follow the SmPC or local guidance.
- Add height above to see the ideal body weight result too.