Creatinine Clearance Calculator

Understanding Creatinine Clearance

Creatinine clearance (CrCl) is a measure of how well the kidneys filter creatinine from the blood. It serves as an estimate of glomerular filtration rate (GFR) and is widely used for adjusting medication doses in patients with impaired kidney function.

The Cockcroft-Gault Equation

This calculator uses the Cockcroft-Gault equation, published in 1976:

The equation accounts for the fact that creatinine production decreases with age and is lower in females due to less muscle mass.

CKD Stages Based on GFR

Stage	GFR (mL/min/1.73m2)	Description
1	90 or higher	Normal kidney function
2	60-89	Mildly decreased
3a	45-59	Mild to moderate decrease
3b	30-44	Moderate to severe decrease
4	15-29	Severely decreased
5	Less than 15	Kidney failure

Clinical Applications

Drug Dosing

Many medications are primarily eliminated by the kidneys and require dose adjustments in renal impairment. Examples include:

• Antibiotics (aminoglycosides, vancomycin, fluoroquinolones)
• Anticoagulants (enoxaparin, dabigatran)
• Diabetes medications (metformin, gliclazide)
• Cardiac medications (digoxin, ACE inhibitors)
• Pain medications (gabapentin, pregabalin)

Contrast Administration

CrCl is assessed before administering iodinated contrast media to evaluate the risk of contrast-induced nephropathy.

Limitations

• Less accurate in extremes of body weight (obese or malnourished)
• Not validated in acute kidney injury
• May overestimate GFR in elderly patients
• Affected by muscle mass variations
• Some medications interfere with creatinine measurement

Weight Considerations

In obese patients, some clinicians recommend using:

• Actual body weight for drug dosing (most common)
• Ideal body weight to avoid overestimation
• Adjusted body weight as a compromise