nephrology & metabolismformula

Cockcroft-Gault Creatinine Clearance

The Cockcroft-Gault equation estimates creatinine clearance from age, weight, sex, and serum creatinine. It is the standard formula referenced by most drug labels for renal dose adjustments, and gives an estimate in mL/min (not normalised to BSA).

inputs

years
Use actual body weight (or adjusted/ideal body weight per protocol)

✓ when to use

Use specifically when a drug label or formulary specifies dose adjustment based on CrCl (Cockcroft-Gault). Many older drugs (DOACs, metformin, lithium, aminoglycosides, vancomycin, enoxaparin) reference CrCl rather than CKD-EPI eGFR. The key difference: CrCl uses actual body weight and is NOT normalised to body surface area, whereas eGFR is normalised to 1.73 m².

✗ when not to use

Cockcroft-Gault is inaccurate in extremes of body weight (obesity, cachexia) — consider using adjusted body weight or ideal body weight depending on institutional protocol. Unreliable in AKI (creatinine not at steady state), pregnancy, and advanced CKD (overestimates GFR due to tubular creatinine secretion). Not recommended for CKD staging — use CKD-EPI eGFR instead.

clinical pearls

  • The critical clinical distinction: CKD-EPI eGFR is for CKD staging; Cockcroft-Gault CrCl is for drug dosing when the label specifies CrCl. These can give meaningfully different numbers, especially in obese, elderly, or very thin patients.
  • In obese patients, using actual body weight in Cockcroft-Gault overestimates CrCl. Many pharmacists use adjusted body weight: AdjBW = IBW + 0.4 × (actual − IBW). Check your institutional protocol.
  • For DOACs (apixaban, rivarelbam, edoxaban, dabigatran), dose adjustments are based on CrCl (Cockcroft-Gault), not eGFR. Using eGFR may lead to inappropriate dosing, particularly in elderly patients where eGFR > CrCl.
  • Cockcroft-Gault systematically overestimates GFR in older adults because it relies on serum creatinine, which decreases with age-related muscle loss. An 85-year-old with 'normal' creatinine may have significantly reduced GFR.
  • The equation uses creatinine in mg/dL. If your lab reports µmol/L, divide by 88.4 to convert. Unit mismatch is a common source of medication dosing errors.

related tools

ckd-epi-2021eGFR for CKD staging (not drug dosing)bmiAssess if weight adjustment needed for obese patients