Estimated Glomerular Filtration Rate
eGFR· also: GFR, Estimated GFR
Clinical Overview
eGFR estimates the volume of blood filtered by the kidneys per minute, calculated from serum creatinine, age, sex, and race. It is the best single measure of overall kidney function and is used to stage chronic kidney disease (CKD) from G1 (>90 mL/min, normal) to G5 (<15 mL/min, kidney failure).
Why This Test Matters
eGFR is the primary measure used to detect, stage, and monitor chronic kidney disease. It also guides drug dosing adjustments — many medications accumulate to toxic levels when eGFR is below 30–60 mL/min (metformin, certain antibiotics, direct anticoagulants, contrast dye). A progressive decline in eGFR over years, even within the normal range, may indicate subclinical CKD.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 90 – 120 | mL/min/1.73m² | CKD G1 (normal or high) ≥90 |
| Adults (18–64) | 60 – 89 | mL/min/1.73m² | CKD G2 (mildly decreased) |
| Elderly (65+) | 45 – 90 | mL/min/1.73m² | Physiologically declines ~1 mL/min/year after age 40 |
Critical (Panic) Values
Critical Low: < 15 mL/min/1.73m². Values outside these limits require immediate clinical attention.
What Causes Abnormal Results?
High eGFR Causes
- High muscle mass (more creatinine production, formula may overestimate)
- Hyperfiltration in early diabetes or pregnancy
Low eGFR Causes
- Chronic kidney disease (diabetes, hypertension most common causes)
- Acute kidney injury
- Glomerulonephritis
- Polycystic kidney disease
- Nephrotoxic medications (NSAIDs, contrast, aminoglycosides)
- Obstruction (kidney stones, enlarged prostate)
Signs & Symptoms to Watch For
How to Prepare for This Test
No special preparation for the blood draw. Avoid creatine supplements and high meat intake the day before.
Factors That Can Affect Results
- Muscle mass (high muscle mass → higher creatinine → lower eGFR estimate)
- Amputation or muscle-wasting disease (low creatinine → overestimates eGFR)
- Race/ethnicity (CKD-EPI 2021 equation removed race coefficient — now race-free)
- Acute changes in kidney function (eGFR lags behind creatinine changes)
- Cimetidine and trimethoprim (block tubular secretion of creatinine, falsely lowering eGFR)
Related Topics
Frequently Asked Questions
What eGFR level requires dialysis?
Dialysis is typically initiated when eGFR falls to 5–10 mL/min/1.73m² with symptoms of uremia (nausea, confusion, fluid overload, pericarditis), or when eGFR is below 15 mL/min/1.73m² in diabetic patients. There is no fixed threshold — the decision depends on symptoms, rate of decline, and patient preference. Pre-emptive kidney transplantation (without dialysis) is the preferred treatment when a suitable donor is available.
Is eGFR accurate in everyone?
eGFR is an estimate with known limitations. It is less accurate at eGFR values above 60 mL/min (overestimates variability), in patients with extremes of muscle mass (bodybuilders or severely malnourished), amputees, and people on vegetarian diets (less dietary creatinine production). In these cases, cystatin C — a protein produced at a more constant rate than creatinine — provides a more accurate eGFR estimate.