eGFR in Blood Test: What It Is & Why It Matters
eGFR (estimated glomerular filtration rate) is a blood test that measures how well your kidneys are filtering waste from your blood. It is calculated using your serum creatinine level, age, sex, and sometimes race. Today, eGFR remains the standard first-line screening for chronic kidney disease (CKD) and is reported automatically whenever a creatinine test is ordered in the United States. A normal eGFR is typically 90 mL/min/1.73 m² or higher, but values decline naturally with age. Understanding your eGFR helps you catch kidney problems early, manage risk factors like diabetes and hypertension, and guide treatment decisions.
What Is eGFR and How Is It Calculated?
eGFR stands for estimated glomerular filtration rate. The glomeruli are tiny filters in your kidneys that remove waste products. The eGFR calculation uses a formula—most commonly the CKD-EPI equation (updated today)—that takes into account your blood creatinine level, age, sex, and race. The CKD-EPI equation removed the race coefficient to reduce health disparities. The result is a number that represents how many milliliters of blood your kidneys filter per minute, adjusted for body surface area.
Why Is eGFR Important?
eGFR is the most reliable indicator of kidney function available from a routine blood test. It is used to stage CKD, monitor disease progression, and adjust medication dosages for drugs cleared by the kidneys. A declining eGFR signals that your kidneys are losing function, often before symptoms appear.
Normal eGFR Ranges by Age )
Kidney function naturally declines with age. The table below summarizes typical eGFR values for healthy adults in the United States.
| Age Group | Normal eGFR Range (mL/min/1.73 m²) | Interpretation |
|---|---|---|
| 20–30 years | ≥ 90 | Normal kidney function |
| 30–40 years | 85–120 | Normal; slight decline with age |
| 40–50 years | 75–110 | Normal; expected decline |
| 50–60 years | 60–100 | Normal; may be lower if other risk factors present |
| 60–70 years | 55–90 | Normal; monitor if trending down |
| 70+ years | 45–85 | Normal; lower values may still be acceptable if stable |
Note: A single eGFR below 60 for three months or more indicates chronic kidney disease (CKD).
eGFR and Chronic Kidney Disease (CKD) Stages
eGFR is used to classify CKD into five stages:
- Stage 1: eGFR ≥ 90 with kidney damage (e.g., protein in urine) – normal function but treat underlying cause.
- Stage 2: eGFR 60–89 with kidney damage – mild loss.
- Stage 3a: eGFR 45–59 – moderate loss.
- Stage 3b: eGFR 30–44 – more significant loss.
- Stage 4: eGFR 15–29 – severe loss; prepare for dialysis or transplant.
- Stage 5: eGFR < 15 – kidney failure; dialysis or transplant needed.
Regular eGFR testing every 3–12 months is recommended for patients with diabetes, hypertension, cardiovascular disease, or a family history of kidney failure.
Factors That Can Affect eGFR Results
Several factors can temporarily alter eGFR without permanent kidney damage:
Diet and Hydration
Eating a large meal of cooked meat, dehydration, or high-sodium intake can raise creatinine, lowering eGFR. Always follow your doctor's instructions for fasting or avoiding certain foods before the test.
Medications
NSAIDs (ibuprofen, naproxen), ACE inhibitors, and some antibiotics can affect creatinine levels. Inform your clinician about all medications and supplements.
Acute Illness
Infections, fever, or vomiting can cause a temporary drop in eGFR. Repeat testing after recovery is often needed to confirm baseline function.
How to Prepare for an eGFR Blood Test
Preparation is simple: eat and drink normally unless your doctor advises otherwise. Avoid strenuous exercise for 24 hours before the test, as it can raise creatinine. Make sure your lab knows your correct age, sex, and race (if using older formulas) to ensure accurate calculation. The test is a standard blood draw from a vein in your arm and takes only a few minutes.
When to Talk to Your Doctor About Your eGFR
If your eGFR is below 60 on two tests separated by at least three months, your doctor will diagnose CKD and discuss further evaluation, including urine albumin-to-creatinine ratio (UACR) and imaging. Even if your eGFR is normal but you have risk factors (diabetes, high blood pressure, family history), ask about annual screening. Early detection can slow progression and prevent complications.
At LabProviders.com, we offer comprehensive kidney function testing that includes eGFR, creatinine, BUN, and UACR. Our CLIA-certified labs provide fast, accurate results with easy online ordering. Take control of your kidney health today—order your kidney function test now.
Take charge of your kidney health today. Order your eGFR blood test from LabProviders.com and get results quickly, securely, and affordably.
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