GFR Calculator – Glomerular Filtration Rate (eGFR)
Calculate eGFR to assess kidney function and CKD stage
How to Use
- Obtain serum creatinine from blood test
- Enter creatinine value with appropriate unit
- Enter patient age
- Select patient sex
- Select race (affects calculation)
- Click calculate to see eGFR result
What is GFR?
Glomerular Filtration Rate (GFR) is the best overall indicator of kidney function. It measures how much blood passes through the glomeruli (kidney filters) each minute. Since direct measurement of GFR is complex, estimated GFR (eGFR) is calculated using serum creatinine, age, sex, and race.
Normal eGFR is 90 or higher. Values below 60 for three months or more indicate chronic kidney disease (CKD). Values below 15 indicate kidney failure requiring dialysis or transplant.
Chronic Kidney Disease Stages
| Stage | eGFR | Description | Treatment |
|---|---|---|---|
| 1 | ≥90 | Normal or high with kidney damage | Monitor, control BP and blood sugar |
| 2 | 60-89 | Mild decrease | Estimate progression, treat complications |
| 3a | 45-59 | Mild to moderate decrease | Evaluate and treat complications |
| 3b | 30-44 | Moderate to severe decrease | Nephrology referral recommended |
| 4 | 15-29 | Severe decrease | Prepare for renal replacement therapy |
| 5 | <15 | Kidney failure | Dialysis or transplant if uremic |
CKD-EPI 2021 Equation
This calculator uses the CKD-EPI 2021 equation, which removed the race coefficient present in earlier versions. The equation provides more accurate eGFR estimates across diverse populations.
The equation uses serum creatinine (waste product from muscle metabolism), age, and sex. Lower creatinine indicates better kidney function, as healthy kidneys efficiently filter it from blood.
Factors Affecting eGFR
- Age: GFR naturally declines with age
- Muscle mass: Higher muscle mass increases creatinine production
- Diet: High protein intake can temporarily elevate creatinine
- Medications: Some drugs affect creatinine secretion
- Dehydration: Can artificially lower eGFR
- Acute kidney injury: Causes sudden eGFR drops
- Chronic conditions: Diabetes, hypertension, heart disease
- Body size: Very large or small individuals may have inaccurate estimates
Frequently Asked Questions
- What does my eGFR number mean?
- eGFR above 90 is normal. 60-89 suggests mild kidney disease. 45-59 is moderate decrease. 30-44 is moderate to severe decrease. 15-29 is severe decrease. Below 15 is kidney failure. Consult your doctor for interpretation based on your complete medical history.
- How often should I check my eGFR?
- For people with CKD, eGFR should be checked at least annually. More frequent monitoring (every 3-6 months) is recommended for stages 3-5, diabetes, or rapidly declining function. Your healthcare provider will determine the appropriate schedule.
- Can eGFR improve over time?
- Yes, eGFR can improve with treatment of underlying causes, better blood pressure and diabetes control, lifestyle changes (diet, exercise, weight loss), and avoiding nephrotoxic medications. However, advanced kidney disease is often irreversible.
- What's the difference between eGFR and creatinine clearance?
- eGFR is estimated from blood creatinine using an equation. Creatinine clearance measures actual kidney filtration using 24-hour urine collection. eGFR is more convenient and correlates well with actual GFR in most patients, making it the preferred screening test.