Nephrology
Creatinine Clearance (Cockcroft-Gault)
Estimated creatinine clearance for drug dosing.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The Cockcroft-Gault equation estimates creatinine clearance (CrCl) from age, weight, serum creatinine and sex, as a surrogate for kidney function. It predates modern eGFR equations and gives an absolute clearance (mL/min) rather than a body-surface-area-indexed value. Because much historical drug-dosing evidence was developed using this method, many medicines specify Cockcroft-Gault creatinine clearance for renal dose adjustment. A correction factor multiplies the result by 0.85 for women.
Interpreting the result
Lower values indicate reduced clearance: a CrCl of 60 mL/min or above is broadly normal to mildly reduced, 30–59 mL/min is moderately reduced and below 30 mL/min is severely reduced. For renally cleared medicines, dose adjustment thresholds are commonly framed around these bands, so the estimate directly affects dosing decisions. Because it is an estimate, it should be checked against the specific drug's Summary of Product Characteristics (SmPC) for the exact threshold to apply.
Worked example
A patient with a stable creatinine and a Cockcroft-Gault CrCl of about 45 mL/min sits in the moderately reduced band. For a renally cleared medicine this would prompt review of the SmPC to confirm whether dose adjustment is needed at that clearance.
Critical actions
Creatinine must be in mg/dL (divide a µmol/L value by 88.4). Consider using ideal or adjusted body weight in obesity. Always verify against the drug's SmPC.
Pearls / pitfalls
- Serum creatinine must be entered in mg/dL; divide a µmol/L value by 88.4 to convert before calculating.
- In obesity, use ideal or adjusted body weight rather than actual weight to avoid overestimating clearance.
- The estimate is unreliable when creatinine is changing rapidly (acute kidney injury) and at extremes of muscle mass.
- Cockcroft-Gault and CKD-EPI eGFR are not interchangeable — always follow the method specified by the individual drug.
Evidence & validation
Published by Cockcroft and Gault in 1976, the equation remains the reference method for renal drug dosing in many drug licences and pharmacology references, even though CKD-EPI eGFR is preferred for staging chronic kidney disease.
Frequently asked questions
Why use Cockcroft-Gault instead of eGFR for drug dosing?
Much of the dosing evidence in drug licences was derived using Cockcroft-Gault creatinine clearance. Many SmPCs therefore specify it, so it is used where the drug guidance references it.
What units does the creatinine need to be in?
The classic equation uses serum creatinine in mg/dL. To convert a µmol/L result, divide by 88.4 before calculating.
Which weight should I use in obese patients?
Using actual body weight can overestimate clearance in obesity, so ideal or adjusted body weight is generally preferred. Follow local or product-specific guidance.
Is Cockcroft-Gault accurate in acute kidney injury?
No. Like other creatinine-based estimates, it is unreliable when creatinine is rising or falling rapidly, because it assumes a steady state.
Can I use eGFR instead?
Sometimes, but not always. eGFR is indexed to body surface area and is used for CKD staging; some drugs are dosed specifically by Cockcroft-Gault. Check the individual drug's recommendation.
References
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31–41.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.
About the creator
Cockcroft & Gault
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