Creatinine Clearance
(Cockcroft-Gault Equation)

Calculates CrCl according to the Cockcroft-Gault equation.

When to use

  • Assessing a patient’s renal function.
  • Prescribing a drug that is renally metabolized.

Why use

  • While the Cockcroft-Gault equation is the most well-known and frequently-calculated estimates of GFR (via Creatinine Clearance), other calculators have recently gained attention as better estimates, like the MDRD. (The latter have not been validated in acute renal failure, only patients with chronic kidney disease.)
  • Creatinine clearance is still used as the standard for drug dosing, instead of GFR

Creatine clearance calculator

years

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lbs

mg/dL

The Cockcroft-Gault Equation may be inaccurate depending on a patient’s body weight and BMI; by providing additional height, we can calculate BMI and provide a modified estimate and range.

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Result

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Advice

After calculating a creatinine clearance, providers should consider calculating an actual GFR as well, to determine the staging/severity of a patient’s chronic kidney disease.

CKD stage GFR level (mL/min/1.73 m2)
Stage 1 ≥ 90
Stage 2 60 – 89
Stage 3 30 – 59
Stage 4 15 – 29
Stage 5 < 15

Formula

Cockcroft-Gault CrCl, mL/min = (140 – age) × (weight, kg) × (0.85 if female) / (72 × Cr)

Ideal body weight (IBW), Devine equation:

  • IBW, kg (male) = 50 + [ 2.3 × (height, inches – 60) ]
  • IBW, kg (female) = 45.5 + [ 2.3 × (height, inches – 60) ]

Adjusted body weight (ABW), kg = IBW, kg + 0.4 × (actual body weight, kg – IBW, kg)

Facts and figures

The most common formula for determining creatinine clearance, which estimates glomerular filtration rate (GFR); creatinine clearance may over-estimate GFR by 10-20%, but still remains the standard for drug dosing adjustments.

Based on several papers and expert opinions, we provide adjustments to the Cockcroft-Gault equation based on body weight and BMI, as it appears to become less accurate in weight extremes (underweight and particularly overweight/obesity). As recommended by Brown et al and Winter et al, adjustments and estimates are made as follows:

Underweight BMI <18.5 Calculation uses actual/total body weight (i.e., no adjustment)
Normal weight BMI 18.5-24.9 Calculation uses ideal body weight, range uses actual body weight
Overweight / obese BMI ≥25 Calculation uses adjusted body weight, range uses ideal body weight

Literature

Original/primary reference


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Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31-41. PubMed PMID: 1244564.

Other references


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Winter MA, Guhr KN, Berg GM. Impact of various body weights and serum creatinine concentrations on the bias and accuracy of the Cockcroft-Gault equation. Pharmacotherapy. 2012 Jul;32(7):604-12. doi:10.1002/j.1875-9114.2012.01098.x. Epub 2012 May 10. PubMed PMID: 22576791.



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Brown DL, Masselink AJ, Lalla CD. Functional range of creatinine clearance for renal drug dosing: a practical solution to the controversy of which weight to use in the Cockcroft-Gault equation. Ann Pharmacother. 2013 Jul-Aug;47(7-8):1039-44. doi: 10.1345/aph.1S176. Epub 2013 Jun 11. Review. PubMed PMID: 23757387.