🫘 Creatinine Clearance (Cockcroft-Gault)

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 2 independent reference calculations · how PhDino checks its numbers

Estimating kidney filtration function from age, weight, sex, and a blood creatinine level.

Creatinine is a waste product from normal muscle metabolism that the kidneys filter out of the blood at a fairly steady rate — how quickly the kidneys clear it (creatinine clearance) is a widely used proxy for overall kidney filtration function, since directly measuring filtration rate is far more involved.

The Cockcroft-Gault equation estimates creatinine clearance from a blood creatinine measurement together with age, weight, and sex, rather than requiring a timed urine collection. Age and sex are included because they correlate with typical muscle mass, which affects how much creatinine a person's muscles produce in the first place, independent of kidney function itself.

Key formula

CrCl (mL/min) = ((140 − age) × weight (kg)) ÷ (72 × serum creatinine (mg/dL))
× 0.85 if female

Notes & limitations

• This is one of several kidney-function estimation equations in clinical use (others include MDRD and CKD-EPI) — they don't always agree closely, particularly at extremes of body size or muscle mass, and clinical protocols often specify which equation to use for a given purpose (like drug dose adjustment).
• Serum creatinine itself is affected by factors other than kidney function — muscle mass, diet, and certain medications all shift it — which is a known limitation of creatinine-based kidney function estimates generally, not specific to this particular equation.