GFR (Glomerular Filtration Rate) Calculator
Calculate estimated GFR (eGFR) from serum creatinine using CKD-EPI equation. eGFR estimates kidney function and determines CKD stage. Normal eGFR > 90 mL/min/1.73m².
🏥 Physiology📐 eGFR = 142 x (Scr/kappa)^alpha x (0.9938)^age🧬 Biology
Serum creatinine Scr (mg/dL)
Age (years)
Sex
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| GFR (Glomerular Filtration Rate) Calculator | — | eGFR = 142 x (Scr/kappa)^alpha x (0.9938)^age | mL/min/1.73m² |
Step-by-Step Examples
Example 1
Normal Adult
Male, Scr=1.0 mg/dL, age=40.
- eGFR ≈ 96 mL/min/1.73m²
- G1: Normal kidney function
- No CKD if no other markers of damage
✓ eGFR ≈ 96 — Normal
Example 2
CKD Stage 3a
Female, Scr=1.5 mg/dL, age=65.
- eGFR ≈ 42 mL/min/1.73m²
- G3a: Mildly-moderately decreased
- Monitor for CKD complications
✓ eGFR ≈ 42 — CKD G3a
Example 3
Kidney Failure
Male, Scr=5.0, age=55.
- eGFR ≈ 11 mL/min/1.73m²
- G5: Kidney failure
- Dialysis or transplant planning
✓ eGFR ≈ 11 — Kidney failure
Real-World Applications
Nephrology
eGFR diagnoses CKD, guides medication dosing, determines dialysis timing.
Pharmacology
Drug dosing adjustments required when eGFR <60 for many medications.
Population Health
eGFR screening identifies CKD in diabetic and hypertensive patients.
Research
eGFR is primary endpoint in clinical trials of CKD progression.
Common Mistakes to Avoid
⚠️
Using MDRD instead of CKD-EPI
CKD-EPI 2021 is more accurate, especially at higher GFR. MDRD underestimates eGFR > 60. Use CKD-EPI for current clinical practice.
⚠️
Acute changes not reflected
Creatinine changes lag GFR changes by 24-48h during AKI. eGFR equations assume stable chronic state.
⚠️
Muscle mass affects creatinine
Low muscle mass (elderly, amputees, liver disease) gives falsely low creatinine and overestimated eGFR. Use cystatin C for these patients.
Frequently Asked Questions
What is GFR? ▾
Volume of blood filtered by glomeruli per minute per 1.73m² body surface area. Best single measure of kidney function. Normal: 90-120 mL/min/1.73m².
What are the CKD stages? ▾
G1: ≥90 (normal). G2: 60-89 (mild). G3a: 45-59. G3b: 30-44. G4: 15-29 (severe). G5: <15 (kidney failure/ESRD).
What is creatinine? ▾
Waste product of muscle creatine phosphate metabolism. Freely filtered by glomerulus, not reabsorbed. Creatinine rises as GFR falls.
How often should eGFR be monitored? ▾
CKD G1-2: annually. G3: every 6-12 months. G4-5: every 1-3 months. More frequent in diabetics or rapidly declining eGFR.
What drugs require dose adjustment with low eGFR? ▾
Metformin (hold if eGFR<30), many antibiotics (gentamicin, vancomycin), anticoagulants (LMWH, DOACs), pain medications (NSAIDs contraindicated <30).