Creatinine Clearance Calculator
Compute creatinine clearance using validated scientific equations. See step-by-step derivations, unit analysis, and reference values.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
CrCl = [(140 - Age) x Weight] / (72 x SCr) x 0.85 (if female)
Where CrCl = Creatinine Clearance in mL/min, Age = patient age in years, Weight = actual body weight in kg, SCr = serum creatinine in mg/dL. The 0.85 correction for females accounts for lower muscle mass. This is the Cockcroft-Gault equation, widely used for drug dosing adjustments.
Worked Examples
Example 1: Male Patient Drug Dosing
Problem:A 65-year-old male weighing 80 kg has a serum creatinine of 1.4 mg/dL. Calculate CrCl for drug dosing.
Solution:CrCl = [(140 - 65) x 80] / (72 x 1.4)\nCrCl = [75 x 80] / 100.8\nCrCl = 6,000 / 100.8\nCrCl = 59.5 mL/min\nThis falls in CKD Stage 3a range, requiring dose adjustment for renally-cleared medications.
Result:CrCl: 59.5 mL/min — Moderate kidney impairment, dose adjustment needed for many drugs
Example 2: Female Patient Kidney Assessment
Problem:A 50-year-old female weighing 60 kg has a serum creatinine of 0.9 mg/dL. Assess kidney function.
Solution:CrCl = [(140 - 50) x 60] / (72 x 0.9) x 0.85\nCrCl = [90 x 60] / 64.8 x 0.85\nCrCl = 5,400 / 64.8 x 0.85\nCrCl = 83.3 x 0.85 = 70.8 mL/min\nThis indicates mildly reduced kidney function (CKD Stage 2).
Result:CrCl: 70.8 mL/min — Mild kidney impairment, monitor and manage risk factors
Frequently Asked Questions
What is creatinine clearance and why is it important?
Creatinine clearance (CrCl) is a measure of how well the kidneys filter creatinine, a waste product of muscle metabolism, from the blood. It serves as a surrogate marker for the glomerular filtration rate (GFR), which is the gold standard measure of kidney function. CrCl is critically important for drug dosing, as many medications are eliminated by the kidneys and require dose adjustments when kidney function is impaired. A normal CrCl is approximately 90-140 mL/min for men and 80-125 mL/min for women, declining naturally by about 1 mL/min per year after age 40.
What factors affect serum creatinine levels?
Serum creatinine is primarily affected by muscle mass, which is why levels differ between males and females. Normal ranges are 0.7-1.3 mg/dL for men and 0.6-1.1 mg/dL for women. High-protein diets, creatine supplements, and intense exercise can temporarily increase creatinine. Certain medications like trimethoprim and cimetidine can raise serum creatinine without affecting actual kidney function by blocking tubular secretion. Age-related muscle loss means that even a normal creatinine in an elderly patient may mask significant kidney impairment.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy