GFR Calculator - Calculate Kidney Function
Free GFR calculator to estimate glomerular filtration rate and assess kidney function using the CKD-EPI equation for chronic kidney disease screening
GFR Calculator
Results
What is a GFR Calculator?
A GFR Calculator is a free medical tool that estimates glomerular filtration rate to assess kidney function using the CKD-EPI equation. It calculates how well kidneys filter waste from blood based on serum creatinine, age, gender, and race, helping detect chronic kidney disease early for timely intervention and treatment.
This calculator works for:
- Kidney disease screening - Detect CKD in early stages
- Diabetes management - Monitor kidney function in diabetics
- Hypertension monitoring - Track kidney health with high blood pressure
- Medication dosing - Adjust drug doses based on kidney function
To assess overall kidney health, check out our BMI Calculator to maintain healthy weight which reduces kidney disease risk factors.
For blood pressure monitoring, explore our Blood Pressure Calculator to track cardiovascular health that directly impacts kidney function.
To calculate daily water needs, use our Daily Water Intake Calculator to ensure proper hydration for optimal kidney function.
For diabetes management, try our Calorie Calculator to maintain healthy weight and blood sugar levels protecting kidney health.
How GFR Calculator Works
The calculation uses the CKD-EPI equation:
Where variables include:
- Scr = Serum creatinine in mg/dL
- κ = 0.7 (female) or 0.9 (male)
- α = -0.329 (female) or -0.411 (male)
- Gender = 1.018 (female) or 1.0 (male)
- Race = 1.159 (African American) or 1.0 (other)
GFR measures kidney filtration capacity in mL/min/1.73m². Normal GFR is 90+ mL/min. Values below 60 for 3+ months indicate chronic kidney disease. Creatinine is a waste product from muscle metabolism filtered by kidneys.
Key Concepts Explained
Glomerular Filtration
Process where kidneys filter blood through glomeruli, removing waste and excess fluid. GFR measures this filtration efficiency.
Serum Creatinine
Waste product from muscle metabolism. High levels indicate reduced kidney function as kidneys can't filter effectively.
CKD Stages
Stage 1 (90+), Stage 2 (60-89), Stage 3 (30-59), Stage 4 (15-29), Stage 5 (<15). Lower GFR indicates worse kidney function.
CKD-EPI Equation
Most accurate GFR estimation formula. Considers age, gender, race, and creatinine for precise kidney function assessment.
How to Use This Calculator
Enter Age
Input your current age in years. GFR naturally declines with age, affecting calculations.
Select Gender and Race
Choose biological gender and race as these factors affect creatinine production and GFR calculation.
Input Creatinine Level
Enter serum creatinine from blood test in mg/dL. This is the key indicator of kidney function.
Get Results
View eGFR value, CKD stage, kidney function status, and interpretation for medical discussion.
Benefits of Using This Calculator
- • Early CKD Detection: Identify kidney disease in early stages when treatment is most effective and damage reversible.
- • Accurate CKD-EPI Formula: Uses most current and accurate equation recommended by kidney disease guidelines.
- • Monitor Disease Progression: Track kidney function changes over time to assess treatment effectiveness.
- • Medication Dosing: Determine appropriate drug doses based on kidney function to prevent toxicity.
- • Risk Assessment: Evaluate cardiovascular disease risk as kidney function correlates with heart health.
- • Free Screening Tool: Calculate GFR instantly without medical appointment for preliminary assessment.
Factors That Affect Your Results
1. Muscle Mass
Higher muscle mass increases creatinine production, potentially underestimating GFR. Athletes may have falsely low GFR values.
2. Diet and Hydration
High protein diet or dehydration temporarily elevates creatinine. Fast before testing and maintain normal hydration for accuracy.
3. Medications
Certain drugs affect creatinine levels or kidney function. NSAIDs, ACE inhibitors, and antibiotics can alter GFR readings.
4. Acute Illness
Fever, infection, or acute kidney injury temporarily reduces GFR. Retest after recovery for accurate baseline assessment.
5. Age-Related Decline
GFR naturally decreases 1 mL/min per year after age 40. Lower values in elderly may be normal aging, not disease.
Frequently Asked Questions (FAQ)
Q: What is a normal GFR level?
A: Normal GFR is 90 mL/min/1.73m² or higher. GFR 60-89 indicates mild kidney damage, 30-59 is moderate, 15-29 is severe, and below 15 is kidney failure. GFR naturally declines with age, decreasing about 1 mL/min per year after age 40.
Q: How is GFR calculated?
A: GFR is calculated using the CKD-EPI equation based on serum creatinine, age, gender, and race. The formula estimates kidney filtration rate without requiring 24-hour urine collection. Blood creatinine levels inversely correlate with kidney function.
Q: What causes low GFR?
A: Low GFR indicates reduced kidney function from diabetes, high blood pressure, glomerulonephritis, polycystic kidney disease, or prolonged urinary obstruction. Dehydration, certain medications, and acute kidney injury can temporarily lower GFR.
Q: Can GFR be improved?
A: GFR can improve with proper management of underlying conditions. Control blood pressure and blood sugar, maintain healthy weight, avoid nephrotoxic medications, stay hydrated, and follow low-sodium diet. Early intervention prevents further kidney damage.
Q: How often should GFR be checked?
A: Check GFR annually if you have diabetes, high blood pressure, or family history of kidney disease. Those with known kidney disease need testing every 3-6 months. Frequency depends on CKD stage and risk factors.