What is this test?
The Cockcroft–Gault equation estimates creatinine clearance from serum creatinine together with age, sex and body weight. It is often used for medicine dosing, but it is not the same as laboratory eGFR and is not a measured 24-hour urine creatinine clearance.
Why might it be ordered?
- To support dose adjustment for medicines cleared by the kidneys.
- When a clinician needs Cockcroft–Gault creatinine clearance rather than eGFR.
What sample is needed?
A serum creatinine result plus accurate age, sex and current body weight are required. No 24-hour urine collection is part of this calculation.
How should you prepare?
Provide an accurate current weight and tell the clinician about recent acute illness, dehydration, unusual muscle mass or rapidly changing kidney function.
How should you understand the result?
The estimate is reported in mL/min and may differ from eGFR. The choice of actual, ideal or adjusted body weight can materially change the result, especially at weight extremes.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.
- Laboratory Tests — MedlinePlus, U.S. National Library of Medicine
- How to Prepare for a Lab Test — MedlinePlus, U.S. National Library of Medicine
- How to Understand Your Lab Results — MedlinePlus, U.S. National Library of Medicine
- Cockcroft-Gault Equation for Estimating Creatinine Clearance — National Kidney Foundation