🧪 Renal Function Tool
Creatinine Clearance & eGFR Calculator
Estimate kidney function using Cockcroft-Gault (CrCl) and MDRD (eGFR) equations. Critical for adjusting medication doses in patients with renal impairment.
mg/dL (normal: 0.6–1.2 mg/dL)
Affects MDRD eGFR only
CrCl (Cockcroft-Gault)
—
mL/min
eGFR (MDRD)
—
mL/min/1.73m²
💊 Dose Adjustment Guidance
📋 Formulas Used
Cockcroft-Gault (CrCl)
CrCl = [(140 − Age) × Weight(kg)] ÷ [72 × SCr(mg/dL)] × (0.85 if female)
Standard formula for medication dose adjustment. Uses ideal body weight in obese patients. Most drug package inserts reference this formula.
MDRD (eGFR) — 4-variable equation
eGFR = 175 × SCr^−1.154 × Age^−0.203 × 0.742(female) × 1.212(Black)
Used for CKD staging. Reports normalized to 1.73 m² BSA. Less accurate at higher GFR levels (>60). The CKD-EPI equation is newer but MDRD remains widely used.
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Frequently Asked Questions
What is creatinine clearance used for in nursing? +
Creatinine clearance (CrCl) is the primary metric used to adjust medication doses in patients with kidney disease. Many drugs — including antibiotics (vancomycin, gentamicin), anticoagulants (heparin, enoxaparin), and cardiac drugs (digoxin) — are renally cleared and must be dose-reduced or avoided when kidney function is impaired. CrCl helps nurses verify that ordered doses are safe for the patient's current renal function.
What's the difference between CrCl and eGFR? +
CrCl (Cockcroft-Gault) estimates how much blood the kidneys filter per minute in absolute terms (mL/min) and is preferred for drug dosing. eGFR (MDRD or CKD-EPI) is normalized to a standard body surface area of 1.73 m² and is used for CKD staging and monitoring kidney disease progression over time. For clinical decision-making with medications, always use the CrCl from Cockcroft-Gault.
Should I use actual body weight or ideal body weight? +
For Cockcroft-Gault: use actual body weight if the patient is at or below ideal body weight. If the patient is obese (BMI >30), use the adjusted body weight (IBW + 0.4 × [actual − IBW]) to avoid overestimating kidney function, which could lead to excessive drug dosing. This calculator uses the entered weight directly — enter IBW or adjusted weight for obese patients when appropriate.
What CrCl level requires dose adjustment for common drugs? +
Thresholds vary by drug, but general guidelines: CrCl <60 mL/min — monitor closely, reduce dose of some drugs; CrCl <30 mL/min — significant dose reduction required for most renally-cleared drugs; CrCl <15 mL/min (ESRD) — many drugs are contraindicated. Specific drugs: vancomycin requires AUC-guided dosing; metformin is contraindicated below 30 mL/min; digoxin requires dose reduction below 50 mL/min. Always consult drug package inserts and clinical pharmacy.
Why does race affect the MDRD equation? +
The original MDRD study found that Black patients had higher serum creatinine at equivalent GFR levels, attributed to higher average muscle mass. The 1.212 multiplier corrects for this. However, race-based correction in medicine is now controversial, and the newer CKD-EPI 2021 equation removes the race variable. Some institutions have switched to CKD-EPI 2021 — check your hospital's protocol. This calculator includes MDRD with the race correction for reference.