Is a Higher or Lower Glomerular Filtration Rate (GFR) Better for Your Health?
Understanding GFR: What It Really Tells You About Kidney Function
The glomerular filtration rate (GFR) is one of the most reliable indicators of how well your kidneys are working. Think of it as your body's natural "waste-removal efficiency score." A higher GFR generally means your kidneys are effectively filtering blood, removing metabolic waste, excess fluids, and toxins—keeping your internal environment balanced and healthy. Conversely, a lower GFR suggests reduced filtration capacity, which may signal early kidney stress, declining function, or even underlying disease.
Why eGFR Is Used Instead of Direct GFR Measurement
In clinical practice, measuring true GFR requires complex, time-intensive procedures like inulin clearance—rarely feasible in routine care. That's why healthcare providers rely on the estimated glomerular filtration rate (eGFR), a highly validated calculation based on serum creatinine levels, age, sex, and race-adjusted equations (such as the CKD-EPI formula). This non-invasive, lab-friendly metric gives doctors a practical, real-world snapshot of kidney health.
What's Considered a "Normal" eGFR?
For most healthy adults, a normal eGFR falls at or above 90 mL/min/1.73 m². Some younger, highly fit individuals—even those in their 20s or 30s—may register values in the 100–120 range, reflecting optimal renal reserve. Importantly, eGFR naturally declines with age (about 0.5–1 mL/min/year after age 40), so "normal" is always interpreted in context—not just as a number, but alongside symptoms, medical history, and other lab markers like urine albumin-to-creatinine ratio (UACR).
When Low eGFR Warrants Medical Attention
An eGFR consistently below 60 mL/min/1.73 m² for three months or longer meets the diagnostic criteria for chronic kidney disease (CKD)—even if you feel perfectly fine. Early-stage CKD often has no noticeable symptoms, making routine screening essential, especially for people with diabetes, hypertension, cardiovascular disease, or a family history of kidney failure. Values under 30 indicate significantly impaired function and require prompt nephrology referral and comprehensive management to slow progression and prevent complications like anemia, bone mineral disorders, or fluid overload.
Can eGFR Be Too High? Understanding the Exceptions
While a high eGFR is typically reassuring, it's not always a sign of superior health. In certain situations—such as pregnancy, uncontrolled type 1 diabetes (early hyperfiltration phase), or severe muscle wasting—eGFR can be artificially elevated due to physiological changes or assay limitations. That's why clinicians never rely on eGFR in isolation; they always correlate it with creatinine trends, cystatin C testing (when indicated), imaging, and clinical presentation.
Taking Action: What to Do With Your eGFR Results
Your eGFR isn't just a lab value—it's actionable intelligence. If yours is within the normal range, focus on kidney-protective habits: maintain healthy blood pressure (<130/80 mmHg), control blood sugar (A1c <7% for diabetics), stay hydrated, avoid NSAIDs overuse, and limit ultra-processed foods and added sugars. If your eGFR is low—or trending downward—schedule a visit with your primary care provider or a nephrologist. Early intervention can preserve kidney function for years, delay dialysis, and improve long-term quality of life.