Creatinine Clearance (Cockcroft-Gault)

The Cockcroft-Gault formula estimates creatinine clearance, a practical proxy for glomerular filtration and therefore overall kidney filtering capacity. It combines age, body mass, and serum creatinine because creatinine production tends to fall with age, rises with larger muscle mass, and accumulates in the blood when the kidneys clear it less efficiently. The result is not a direct lab measurement; it is a clinical estimate originally designed to help with drug dosing decisions.

Use it when you need a quick estimate of renal function, especially for adjusting medications that are cleared by the kidneys. It is most often applied in adults, and the female adjustment is used because average creatinine production is lower in women due to lower muscle mass.

• Forgetting to multiply the final result by 0.85 for women
• Using serum creatinine in the wrong units instead of mg/dL
• Assuming this is the same as measured GFR rather than an estimate used mainly for dosing