eGFR Calculator: Understanding Your Kidney Function Test Results
Your doctor just mentioned your eGFR number—but what does it actually mean? Learn how to interpret your kidney function test results and what they tell you about your health.
Medical Disclaimer
This article is for educational purposes only and is not medical advice. Always consult with your healthcare provider about your specific test results and health concerns. Do not use this information to diagnose or treat any medical condition.
What is eGFR?
eGFR stands for estimated Glomerular Filtration Rate—it's a number that tells you how well your kidneys are filtering waste from your blood. Think of it as a "kidney efficiency score."
Your kidneys contain about 1 million tiny filters called glomeruli. The GFR measures how much blood passes through these filters each minute. The "estimated" part means it's calculated from a blood test (creatinine) rather than directly measured.
Normal eGFR Ranges
Note: eGFR naturally declines with age, even in healthy kidneys. A slight decrease doesn't automatically mean kidney disease.
Understanding Chronic Kidney Disease (CKD) Stages
Doctors use eGFR to classify kidney disease into five stages. Understanding your stage helps guide treatment and lifestyle changes.
Stage 1: Normal or High Function
eGFR: 90+ mL/min/1.73m²
Kidney function is normal or better than normal, but you may have other signs of kidney damage (protein in urine, structural abnormalities).
Action: Focus on prevention and treating underlying conditions.
Stage 2: Mild Kidney Disease
eGFR: 60-89 mL/min/1.73m²
Slight decrease in kidney function with evidence of kidney damage. Many people don't have symptoms.
Action: Manage blood pressure, blood sugar, and see nephrologist if progressing.
Stage 3: Moderate Kidney Disease
Stage 3a: 45-59 mL/min/1.73m² | Stage 3b: 30-44 mL/min/1.73m²
Moderate decrease in kidney function. May experience fatigue, swelling, urination changes.
Action: Regular nephrologist visits, dietary changes, medication adjustments.
Stage 4: Severe Kidney Disease
eGFR: 15-29 mL/min/1.73m²
Severe decrease in kidney function. Symptoms more noticeable: fatigue, fluid retention, nausea.
Action: Close monitoring, prepare for possible dialysis or transplant.
Stage 5: Kidney Failure (ESRD)
eGFR: Less than 15 mL/min/1.73m²
Kidneys have lost most function. Cannot sustain life without dialysis or transplant.
Action: Dialysis or kidney transplant required.
How is eGFR Calculated?
Your eGFR is calculated from your blood creatinine level along with other factors:
Factors Used in Calculation
Waste product from muscle metabolism. Higher levels indicate reduced kidney function.
Kidney function naturally decreases with age, even in healthy people.
Men typically have higher muscle mass, affecting creatinine baseline levels.
Some equations adjust for differences in muscle mass by ethnicity.
Common Equations Used
CKD-EPI (2021) - Most Common
The most widely used equation, recently updated to remove race adjustments. Considered most accurate for most adults.
MDRD (Modification of Diet in Renal Disease)
Older equation, less accurate at higher GFR levels. Still sometimes used.
Schwartz Equation
Used specifically for children under 18 years old.
What Can Affect Your eGFR Results?
Can Lower eGFR
- Dehydration (temporary decrease)
- High-protein diet or supplements
- Intense exercise before test
- Certain medications (NSAIDs, antibiotics)
- High muscle mass (bodybuilders)
- Recent meat consumption
Can Raise eGFR
- Good hydration
- Lower protein intake
- Pregnancy (increased blood flow)
- Low muscle mass
- Vegetarian/vegan diet
- Young age (higher baseline)
When Should You Be Concerned?
Red Flags That Need Attention
- Rapid decline: eGFR drops more than 5 points in a year
- Below 60: Especially with symptoms or other risk factors
- Protein in urine: Combined with low eGFR indicates kidney damage
- Symptoms: Swelling, fatigue, changes in urination
- Risk factors: Diabetes, high blood pressure, family history
When Not to Panic
- Single abnormal result: Retest before worrying
- Slight decrease with age: Normal aging process
- Above 60 with no symptoms: Often not clinically significant
- Temporary factors: Dehydration, recent exercise can affect results
Calculate Your eGFR
Use our free eGFR calculator to estimate your kidney function based on your creatinine levels and other factors.
How to Protect Your Kidney Health
Lifestyle Strategies
- Stay hydrated: Drink enough water daily
- Control blood pressure: Target < 130/80 mmHg
- Manage blood sugar: Keep A1C < 7% if diabetic
- Maintain healthy weight: Reduces strain on kidneys
- Exercise regularly: 30 min most days
- Don't smoke: Smoking damages blood vessels
Dietary Considerations
- Reduce sodium: Limit to 2,300mg daily
- Monitor protein: Excess protein stresses kidneys
- Limit phosphorus: If eGFR < 45
- Watch potassium: May need restriction in later stages
- Be cautious with NSAIDs: Can damage kidneys
- Consult a dietitian: For personalized kidney diet
The Bottom Line
Your eGFR is a valuable snapshot of kidney function, but it's just one piece of the puzzle. A single result doesn't tell the whole story—your doctor looks at trends over time, other lab values, symptoms, and risk factors.
If your eGFR is concerning, the good news is that early detection and proper management can slow or even stop kidney disease progression. Work with your healthcare team, make recommended lifestyle changes, and monitor your kidney function regularly.