Creatinine Clearance Calculator

What Is Creatinine Clearance?

Creatinine clearance (CrCl) estimates how efficiently your kidneys filter creatinine, a waste product of muscle metabolism, from the blood. It is expressed in mL/min and correlates closely with glomerular filtration rate (GFR). Normal creatinine clearance is approximately 90–140 mL/min for men and 80–125 mL/min for women. This calculator uses the Cockcroft-Gault equation, which factors in serum creatinine, age, weight, and sex.

The Cockcroft-Gault Formula

CrCl = [(140 – age) × weight in kg] / (72 × serum creatinine in mg/dL). For women, multiply the result by 0.85 because women have lower average muscle mass. A 50-year-old man weighing 80 kg with a creatinine of 1.2 mg/dL has a CrCl of about 83 mL/min, within the normal range. This formula is widely used for drug dosing adjustments, particularly for medications that are primarily eliminated by the kidneys.

Creatinine Clearance by Age and Creatinine

The table shows how CrCl falls as age rises and kidney function drops. All rows use the Cockcroft-Gault equation; the female column applies the 0.85 factor.

The pattern matters for dosing. The same creatinine of 2.0 mg/dL that leaves a 40-year-old near the normal range drops a 70-year-old to 32 mL/min, a level where many drugs need reduced doses. Age and weight move the number as much as creatinine does, which is why the flat creatinine value on a lab report can understate kidney impairment in older, lighter patients.

Clinical Applications

Many medications require dose adjustment when CrCl drops below certain thresholds. Antibiotics like vancomycin and aminoglycosides, anticoagulants like enoxaparin, and diabetes medications like metformin all have dosing guidelines tied to creatinine clearance. Pharmacists and physicians use CrCl to determine whether a standard dose is safe or needs reduction. In some cases, medications are contraindicated entirely below specific CrCl levels.

CrCl vs eGFR

Both estimate kidney function but use different formulas. The Cockcroft-Gault equation (CrCl) uses actual body weight and is preferred for drug dosing. The CKD-EPI equation (eGFR) is normalized to body surface area and is preferred for staging chronic kidney disease. In clinical practice, both are used depending on the context: drug prescribing information typically references CrCl, while disease staging uses eGFR.

Frequently asked questions