In shortGFR shows how well the kidneys filter blood. Normal is ≥ 90 mL/min/1.73 m²; CKD staging starts with a persistent drop below 60 for over 3 months. Estimate your GFR from creatinine in the calculator on this page.
What this marker is
GFR (glomerular filtration rate) is the main measure of kidney function: how much blood the kidneys clear per minute. It is not measured directly but calculated from blood creatinine, age and sex — using the CKD-EPI 2021 formula, the current standard.
GFR defines the stage of chronic kidney disease (CKD): the diagnosis is made when GFR stays below 60 mL/min/1.73 m² for over 3 months or other signs of kidney damage are present.
GFR calculator (CKD-EPI 2021)
Enter your age, sex and creatinine from the report — the calculator estimates GFR and the stage.
CKD-EPI 2021 formula (creatinine, race-free) — valid for adults 18+. The calculation runs in your browser; no data is sent anywhere.
Reference ranges and CKD stages
| Group | Reference range |
|---|---|
| G1 — normal | ≥ 90 mL/min/1.73 m² (with no signs of kidney disease) |
| G2 — mildly decreased | 60–89 mL/min/1.73 m² |
| G3a — moderately decreased | 45–59 mL/min/1.73 m² |
| G3b — markedly decreased | 30–44 mL/min/1.73 m² |
| G4 — severely decreased | 15–29 mL/min/1.73 m² |
| G5 — kidney failure | < 15 mL/min/1.73 m² |
GFR declines with age — roughly by 1 mL/min per year after 40; that is physiology. CKD is diagnosed at GFR < 60 for over 3 months or by other signs of kidney damage (protein in urine, ultrasound changes). Ranges differ between laboratories.
Low GFR: possible causes
Chronic kidney diseaseDiabetes and hypertension are the two main causes; then glomerulonephritis, polycystic disease.
Acute kidney injuryDehydration, infections, NSAIDs, contrast — GFR falls fast and often recovers.
Congestive heart failureKidneys get too little blood — filtration drops.
Urinary tract obstructionStones, prostate adenoma — urine cannot drain.
AgeAfter 40, GFR declines by about 1 mL/min a year — without disease.
What can skew the result
These factors can shift the result without any disease — keep them in mind before a retest:
A meat-heavy meal the day before (raises creatinine)Large muscle massNSAIDs and some antibioticsDehydration
How to prepare
Creatinine is taken in the morning, fasting; for 1–2 days avoid heavy meat meals and hard workouts. Details: Preparation: venous blood.
When a retest makes sense
A single decrease is rechecked in 1–3 months: CKD is confirmed only by a drop lasting over 3 months. In CKD, the nephrologist sets the monitoring schedule.
Who usually reviews this result
An out-of-range result is usually reviewed by: Primary care physician, nephrologist. Bring your report and any previous results to the visit.
Names used on lab reports
Look for one of these names on your report:
GFReGFRCKD-EPI
GFReGFRCKD-EPI
Several markers on your report?
The app reads your whole report — this marker together with its neighbors, not one by one.
Frequently asked questions
GFR 58 — is that chronic kidney disease?
A single low value is not a diagnosis: CKD is confirmed at GFR < 60 for over 3 months or by other signs (protein in urine, ultrasound changes). Retest creatinine in 1–3 months and show the result to your physician.
Why is GFR lower in the elderly — is it normal?
With age the kidneys physiologically filter more slowly: after 40, GFR falls by about 1 mL/min a year. So a moderate decrease in the elderly is judged together with urine protein, blood pressure and sugar.
How is GFR different from creatinine?
Creatinine is the raw substance in blood; GFR is the calculated kidney function from creatinine adjusted for age and sex. The same creatinine of 100 µmol/L gives different GFR in a young man and an elderly woman.
Sources
- KDIGO 2024: Clinical Practice Guideline for the Evaluation and Management of CKD — KDIGO (kdigo.org). Accessed: September 17, 2026.
- MedlinePlus — Glomerular filtration rate — MedlinePlus (medlineplus.gov). Accessed: September 17, 2026.