GFR Calculator for Kidney Function

GFR Equation:

\[ eGFR = 142 \times \min(Scr/\kappa, 1)^\alpha \times \max(Scr/\kappa, 1)^{-1.200} \times 0.9938^{age} \times (1.012 \text{ if female}) \]

Estimated GFR (eGFR):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the GFR Calculator for Kidney Function?

The GFR (Glomerular Filtration Rate) Calculator estimates kidney function from serum creatinine, age, and gender. It provides an accurate assessment of how well the kidneys are filtering waste from the blood.

2. How Does the Calculator Work?

The calculator uses the GFR equation:

\[ eGFR = 142 \times \min(Scr/\kappa, 1)^\alpha \times \max(Scr/\kappa, 1)^{-1.200} \times 0.9938^{age} \times (1.012 \text{ if female}) \]

Where:

\( Scr \) — Serum creatinine (mg/dL)
\( \kappa \) — 0.7 (female) or 0.9 (male)
\( \alpha \) — -0.241 (female) or -0.302 (male)
\( age \) — Age in years
1.012 — Female multiplier

Explanation: The equation accounts for the non-linear relationship between creatinine levels and glomerular filtration rate, with different coefficients for different demographic groups.

3. Importance of GFR Calculation

Details: Accurate GFR estimation is essential for assessing kidney health, diagnosing kidney disease stages, monitoring disease progression, and determining appropriate medication dosages for patients with impaired kidney function.

4. Using the Calculator

Tips: Enter serum creatinine in mg/dL, age in years, and select gender. All values must be valid (creatinine > 0, age between 1-120 years). For most accurate results, use creatinine values from fasting blood samples.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal GFR value?
A: Normal GFR is generally ≥90 mL/min/1.73m². Values between 60-89 may indicate early kidney disease, while values below 60 for 3+ months typically indicate chronic kidney disease.

Q2: Why are different coefficients used for males and females?
A: Men typically have higher muscle mass than women, which affects creatinine production. The different coefficients account for these physiological differences to provide accurate GFR estimates.

Q3: When is the best time to measure creatinine?
A: Morning fasting samples are ideal as they minimize dietary influences. Avoid testing after high-protein meals or intense physical activity, which can temporarily elevate creatinine levels.

Q4: What factors can affect GFR accuracy?
A: Extreme age, amputations, pregnancy, rapidly changing kidney function, very high or low muscle mass, and certain medications can affect the accuracy of estimated GFR calculations.

Q5: Can this calculator be used for medication dosing?
A: While estimated GFR is useful for general assessment, for precise drug dosing in patients with significant kidney impairment, measured GFR (using methods like iohexol clearance) may be necessary.