eGFR Blood Test: Normal Ranges, Causes & What Your Results Mean

What Is eGFR?

The estimated glomerular filtration rate (eGFR) is a calculated measure of how efficiently your kidneys filter waste from the blood. It is derived from your serum creatinine level, adjusted for age, sex, and ethnicity using the CKD-EPI equation (the standard in UK laboratories since 2021).

The glomeruli are tiny filtering units in the kidneys — each kidney contains approximately one million. The GFR represents the total volume of fluid filtered by all glomeruli per minute. A healthy young adult typically has a GFR of around 120 mL/min/1.73m², though this naturally declines with age at roughly 1 mL/min/year after age 40.

eGFR is the single most important number for staging chronic kidney disease (CKD) and determining treatment decisions. It is automatically calculated and reported whenever a serum creatinine test is ordered in the UK.

Why Is eGFR Tested?

• CKD screening and staging — eGFR defines CKD stages 1–5 and guides referral to nephrology
• Diabetes monitoring — diabetic nephropathy is the leading cause of end-stage renal disease in the UK
• Hypertension management — kidney function dictates choice of antihypertensive medications
• Drug dosing — many medications (metformin, DOACs, antibiotics) require dose adjustment based on eGFR
• Pre-operative assessment — kidney function affects anaesthetic drug clearance
• Cardiovascular risk assessment — reduced eGFR is an independent risk factor for heart disease

Normal Ranges and CKD Stages

NICE guidelines state that a single eGFR below 60 should be confirmed with a repeat test at least 90 days later before diagnosing CKD.

What Do Low eGFR Levels Mean?

• Chronic kidney disease — the most common cause of persistently reduced eGFR
• Acute kidney injury — sudden drops in eGFR from dehydration, sepsis, or drug toxicity
• Diabetic nephropathy — the leading cause of CKD in the UK
• Hypertensive nephrosclerosis — long-standing high blood pressure damages kidney blood vessels
• Glomerulonephritis — inflammatory conditions affecting the glomeruli
• Polycystic kidney disease — inherited condition causing progressive renal impairment
• Obstruction — kidney stones or enlarged prostate blocking urine flow
• Age-related decline — eGFR naturally decreases with age; many people over 70 have eGFR 60–89 without clinical CKD

What Do High eGFR Levels Mean?

• Generally normal — eGFR above 90 is considered healthy
• Hyperfiltration — eGFR above 120–130 can occur in early diabetes, pregnancy, or high-protein diets and may indicate early kidney stress
• Low muscle mass — less creatinine production artificially inflates eGFR, potentially masking kidney impairment

How to Protect Your Kidney Function

• Control blood pressure — target below 140/90 mmHg (or 130/80 if you have diabetes or CKD)
• Manage blood sugar — tight glycaemic control (HbA1c below 48 mmol/mol) slows diabetic kidney damage
• Stay hydrated — drink 1.5–2 litres of water daily; more in hot weather or during exercise
• Reduce salt intake — aim for under 6g/day as recommended by the NHS
• Avoid nephrotoxic drugs — minimise NSAID use; always check kidney function before starting new medications
• Don't smoke — smoking accelerates kidney disease progression
• Moderate protein intake — if eGFR is below 30, a protein-controlled diet may be recommended

When Should You Get Tested?

• You have diabetes, high blood pressure, or cardiovascular disease
• There is a family history of kidney disease
• You take medications that affect kidney function
• You are over 60 (routine NHS Health Check includes eGFR)
• You have symptoms like swollen ankles, fatigue, or changes in urination

Which Lola Health Tests Include eGFR?

eGFR is automatically calculated whenever creatinine is tested. It is included in Core Health, Vital Check, and Peak Insights panels. Also available as an add-on with any Lola Health blood test.