Summary
eGFR (Estimated Glomerular Filtration Rate) measures how well your kidneys are filtering waste from the blood each minute. It is calculated from serum creatinine, adjusted for age, sex, and ethnicity — and is more accurate than creatinine alone. eGFR is used to diagnose, stage, and monitor chronic kidney disease (CKD) in the UK and internationally.
The glomerular filtration rate is the volume of blood filtered by the kidneys per minute. A normal GFR is approximately 90–120 mL/min/1.73m². eGFR uses the CKD-EPI equation (or MDRD formula) applied to serum creatinine to estimate this value without requiring a 24-hour urine collection.
CKD is defined as eGFR 3 months, or evidence of kidney damage (proteinuria, haematuria, structural abnormality) regardless of eGFR. It is staged G1–G5, with G5 ( 60 does not exclude early kidney disease — proteinuria (urine ACR) is essential to detect early diabetic and hypertensive nephropathy.
What It Is
The Glomerular Filtration Rate (GFR) is the volume of ultrafiltrate produced by all glomeruli per minute — the gold standard measure of kidney function. True GFR measurement requires inulin or iohexol clearance studies; in practice, eGFR is estimated from serum creatinine using validated equations.
The CKD-EPI equation (2009, revised 2021) is the standard in the UK: eGFR = 141 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.209 × 0.993^Age × [1.018 if female]. The 2021 revision removed the race variable. eGFR values > 60 are reliable; values > 90 mL/min/1.73m² are reported as ‘>90’ because the equation is less precise at high filtration rates.
CKD staging by NICE/KDIGO: G1 ≥ 90 (with evidence of kidney damage), G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 < 15.
Functions
Kidney filtration measurement
eGFR quantifies how efficiently the kidneys clear waste from blood — the primary metric of kidney health.
CKD diagnosis and staging
eGFR is used to diagnose CKD and assign a stage (G1–G5) that guides treatment, monitoring frequency, and nephrology referral.
Cardiovascular risk marker
Low eGFR is an independent cardiovascular risk factor — eGFR < 60 approximately doubles the risk of heart disease, stroke, and death.
Drug dosing guide
Many medications are renally cleared — eGFR is used to calculate safe doses of antibiotics, anticoagulants, and other drugs.
Reference Ranges
eGFR — Estimated Glomerular Filtration Rate
Measured in mL/min/1.73m²| Status | Range (mL/min/1.73m²) | What it means |
|---|---|---|
| Severely reduced | < 30 | Severe CKD (G4–G5) — nephrology referral required. Near kidney failure. |
| Moderately reduced | 30–59 | Moderate CKD (G3a–G3b) — active management and regular monitoring needed. |
| Normal/mildly reduced | ≥ 60 | Normal or mildly reduced filtration. In the absence of proteinuria, CKD is unlikely. |
eGFR > 90 is reported as '>90' and is considered normal. Two readings < 60, at least 3 months apart, are required to diagnose CKD. A single low eGFR may be transient (dehydration, AKI). eGFR is less accurate at extremes of body composition.
Symptoms of Imbalance
Reduced eGFR is often entirely asymptomatic until advanced stages — CKD is a silent disease in the majority of affected people.
- Often completely asymptomatic until eGFR < 30
- Fatigue and weakness
- Swollen ankles and legs
- Shortness of breath
- Persistent itching (pruritis uraemia)
- Nausea, vomiting, loss of appetite
- Confusion (uraemic encephalopathy in severe cases)
- High eGFR has no pathological clinical significance
Causes of Imbalance
- Diabetes mellitus (diabetic nephropathy — the leading cause of CKD)
- Hypertension (hypertensive nephrosclerosis)
- Glomerulonephritis (IgA nephropathy, FSGS, membranous nephropathy)
- Polycystic kidney disease (PKD)
- Recurrent urinary tract infections or obstruction
- Ageing — eGFR naturally declines by ~1 mL/min/year from age 40
- NSAIDs, contrast media, aminoglycosides
- High eGFR is not a clinical concern in isolation
- Hyperfiltration from early diabetes may initially cause eGFR > 120 — this is paradoxically harmful to the kidneys long-term
FAQs
A normal eGFR is > 60 mL/min/1.73m², with most healthy adults under 40 having an eGFR > 90. Values of 60–89 are ‘mildly reduced’ and only diagnosed as CKD if kidney damage markers (proteinuria, haematuria) are also present. An eGFR < 60 on two tests at least 3 months apart confirms CKD. eGFR < 30 requires nephrology referral; < 15 indicates kidney failure.
Yes. GFR declines naturally at approximately 1 mL/min/year from around age 40. This means a healthy 70-year-old may have an eGFR of 60–70 mL/min/1.73m² without any kidney disease. The rate of decline is the important variable — a sudden fall of > 5 mL/min/year is considered abnormally rapid and warrants investigation even if the absolute eGFR remains > 60.
Yes — dehydration reduces kidney perfusion, causing pre-renal azotaemia with elevated creatinine and apparent reduction in eGFR. This is typically transient and corrects with rehydration. If your eGFR is unexpectedly low, ensure you were well-hydrated at the time of the test. Two separate tests at least 3 months apart are needed to confirm CKD.
Moderate protein restriction (0.6–0.8 g/kg/day rather than the UK average of 1.2–1.4 g/kg/day) may slow CKD progression by reducing hyperfiltration and the accumulation of nitrogen waste products. However, very low protein diets carry malnutrition risks. NICE recommends dietary advice from a specialist renal dietitian for people with eGFR < 30. Do not self-restrict protein without medical guidance.
Creatinine clearance is measured from a 24-hour urine collection and provides a more direct estimate of GFR. eGFR is a mathematical estimate from a single blood creatinine measurement — far simpler to perform but less accurate at extremes of body composition. For most clinical purposes, eGFR is sufficient. A 24-hour urine collection for creatinine clearance is reserved for patients where precision is critical, such as before living kidney donation.
References
- Levey AS, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604–612. View source
- NICE. Chronic kidney disease: assessment and management. NG203. 2021. View source
- KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1–150. View source