119 Estimated creatinine clearance rate (eClCr)

Creatinine clearance (Cockcroft–Gault): formula, use for drug dosing, strengths and limitations.

The estimated creatinine clearance (eClCr) calculated with the Cockcroft–Gault formula estimates how many millilitres of blood the kidneys clear of creatinine per minute. Unlike eGFR, it uses body weight and is not normalised to body surface area, so it reflects the individual's actual filtering capacity in mL/min. Because many drug-dosing recommendations were developed with this formula, it is still widely used to adjust doses of medicines excreted by the kidneys.

Kidney functionDrug dosingCockcroft–Gault

Normal (young adult)≈ 90–140 mL/min

Moderate impairment30–59 mL/min

Severe impairment15–29 mL/min

UnitmL/min (not per 1.73 m²)

The Cockcroft–Gault formula

CrCl (mL/min) = (140 − age) × weight (kg) / (72 × Scr in mg/dL) × 0.85 (if female)

With creatinine in µmol/L the equivalent is (140 − age) × weight × 1.23 / Scr for men and × 1.04 for women. Example: a 70-year-old woman weighing 60 kg with creatinine 90 µmol/L has CrCl ≈ 70 × 60 × 1.04 / 90 ≈ 49 mL/min, which is moderately reduced, even though her creatinine looks "normal".

Figure 1. Kidney function categories. Creatinine clearance in mL/min is interpreted with similar cut-offs, mainly for drug dosing.

Strengths and limitations

Weight: in obesity, using actual weight overestimates clearance; ideal or adjusted body weight is often used instead
Creatinine: the formula was derived in 1976 before creatinine assays were standardised. Modern assays give lower values, so CrCl tends to be overestimated, especially in older people with low muscle mass.
Stability: like eGFR, it is only valid when kidney function is stable, not in acute kidney injury
Creatinine secretion: because creatinine is partly secreted by the tubules, creatinine clearance is higher than true GFR

Clinical significance

Many medicines must be reduced or avoided when clearance falls. These include some antibiotics, anticoagulants (for example, direct oral anticoagulants), diabetes medicines, digoxin, lithium and some painkillers. A reduced clearance is also a reason to avoid NSAIDs and to take care with contrast media. For diagnosing and staging chronic kidney disease, eGFR (CKD-EPI) and urine albumin are used instead.

What to do

Tell every doctor and pharmacist about reduced kidney function so they can check doses. Do not take over-the-counter painkillers of the NSAID type (ibuprofen, diclofenac, naproxen) regularly without advice.

References

Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31–41. doi:10.1159/000180580
Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int. 2024;105(4S):S117–S314. doi:10.1016/j.kint.2023.10.018
Levey AS, Bosch JP, Lewis JB, et al. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med. 1999;130(6):461–470. PMID: 10075613

This article is for general information and does not replace a consultation with a doctor. Laboratory results must be interpreted by a physician together with symptoms and other tests.

Published on 8 May 2024

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