Creatinine Clearance (Cockcroft-Gault)
Estimate kidney function from age, weight, and creatinine level.
Used to adjust medication doses for kidney health.
The Formula
CrCl = [(140 - age) × weight] / (72 × S_Cr) (× 0.85 for women)
The Cockcroft-Gault equation estimates how well the kidneys filter waste from the blood. It is widely used to adjust medication doses in patients with impaired kidney function.
Variables
| Symbol | Meaning |
|---|---|
| CrCl | Creatinine clearance (mL/min) |
| age | Patient's age (years) |
| weight | Patient's weight (kg). Divide lbs by 2.205. |
| S_Cr | Serum creatinine level (mg/dL) |
| 0.85 | Correction factor for women (lower muscle mass) |
Example 1
A 60-year-old man, 80 kg, serum creatinine 1.2 mg/dL
CrCl = [(140 - 60) × 80] / (72 × 1.2)
CrCl = (80 × 80) / 86.4 = 6400 / 86.4
CrCl ≈ 74.1 mL/min (mildly reduced kidney function)
Example 2
A 45-year-old woman, 65 kg, serum creatinine 0.9 mg/dL
CrCl = [(140 - 45) × 65] / (72 × 0.9) × 0.85
CrCl = (95 × 65) / 64.8 × 0.85 = 6175 / 64.8 × 0.85
CrCl ≈ 80.9 mL/min (normal kidney function)
When to Use It
Use the creatinine clearance formula when:
- Adjusting medication doses for patients with kidney impairment
- Screening for chronic kidney disease
- Monitoring kidney function over time
- Assessing eligibility for certain medical procedures