Creatinine Clearance and eGFR Calculator for Nurses
CKD-EPI 2021 (race-free) and Cockcroft-Gault with IBW/AdjBW support. Transparent calculations.
Common clinical questions about this calculator and its applications
What's the difference between CrCl and eGFR?
Creatinine Clearance (CrCl, Cockcroft-Gault) estimates kidney function based on serum creatinine, age, weight, and sex. eGFR (CKD-EPI 2021) uses creatinine, age, and sex without weight, and is the standard for staging chronic kidney disease. CrCl tends to overestimate GFR in obese patients and is preferred for medication dosing.
Which should I use for medication dosing adjustments?
Most drug dosing guidelines reference Cockcroft-Gault CrCl, especially older medications. However, newer guidelines increasingly use eGFR. Always check the specific drug monograph or your facility's renal dosing protocol. When in doubt, consult pharmacy for renally-cleared medications.
Why does the calculation require weight for CrCl but not eGFR?
Cockcroft-Gault equation incorporates weight because it was designed to estimate actual creatinine clearance. eGFR equations normalize to body surface area (1.73 m²) and don't require weight. This makes eGFR more practical for screening but less precise for individual medication dosing.
How often should renal function be reassessed?
In stable outpatients, every 6-12 months. In hospitalized patients, daily to every few days depending on clinical stability. More frequent monitoring is needed for acute kidney injury, critical illness, or when using nephrotoxic medications. Always use the most recent creatinine value for calculations.
What if creatinine is low but patient is elderly or has low muscle mass?
Low creatinine in elderly or malnourished patients doesn't necessarily mean good kidney function - it may reflect low muscle mass. The Cockcroft-Gault equation accounts for age and weight, which helps, but cystatin C-based equations may be more accurate in these populations. Consider clinical context and trends, not just a single number.
About Our Validation & Sources
All calculators on Nurside use evidence-based formulas from standard clinical practice guidelines. Our validation thresholds are derived from clinical experience, published literature, and expert consultation.
Safety Features: Built-in validation catches common entry errors (like unit confusion), flags unusually high or low values, and requires explicit confirmation for potentially dangerous calculations. This is designed to support, not replace, your clinical judgment.
Formula Transparency: Click "Methods Used" in any calculator to see the exact formula and safety thresholds being applied. We believe you should always understand how your clinical tools work.
Educational Purposes Only: These calculators are provided for educational and clinical support purposes. They do not constitute medical advice and should not replace independent clinical judgment. Always verify calculations against your facility's protocols and the patient's specific clinical context.