eGFR (Estimated Glomerular Filtration Rate): Normal Range, What High & Low Levels Mean

eGFR stands for Estimated Glomerular Filtration Rate. It estimates how efficiently your kidneys are filtering your blood each minute, expressed as millilitres per minute per 1.73 m² of body surface area. Your lab calculates it from your blood creatinine level — creatinine is a natural waste product your muscles produce — combined with your age, sex, and race. Because it uses a formula rather than a direct measurement, the word 'estimated' is part of the name. It is the primary number doctors use to understand kidney function and to stage chronic kidney disease. Talk with your healthcare provider about what your specific eGFR result means for you.

According to the National Kidney Foundation, an eGFR of 90 mL/min/1.73m² or above is associated with normal kidney function in adults. Results between 60 and 89 mL/min/1.73m² suggest mildly reduced function (Stage 2 CKD), while 30 to 59 mL/min/1.73m² reflects moderate reduction (Stage 3 CKD). Severely reduced function falls between 15 and 29 mL/min/1.73m² (Stage 4), and a result below 15 mL/min/1.73m² corresponds to Stage 5, or kidney failure. Keep in mind that eGFR naturally tends to decline with age, so your doctor interprets your result alongside your full health picture. Always discuss your specific number with your healthcare provider to understand what it means for you.

An eGFR above 90 mL/min/1.73m² is considered normal. Values above 120 mL/min/1.73m² may reflect a state called hyperfiltration, where the kidneys are working harder than usual. Hyperfiltration can occur during pregnancy due to natural increases in kidney activity, in the early stages of diabetes before any kidney damage appears, or with high protein intake. Hyperfiltration typically causes no symptoms you would notice on its own. For people with diabetes in particular, monitoring eGFR over time helps detect early kidney involvement. A high reading does not automatically signal a problem, but your healthcare provider is the right person to interpret what your result means for your individual situation.

A low eGFR tells your doctor that your kidneys are filtering blood more slowly than expected. Many things can reduce eGFR. Long-term conditions like diabetes and high blood pressure are the leading causes of chronic kidney disease worldwide. Acute causes include dehydration, certain medications such as NSAIDs or some antibiotics, and urinary tract obstruction. Other contributors include inflammation of the kidney's filtering units (glomerulonephritis), polycystic kidney disease, recurrent kidney infections, and autoimmune conditions like lupus nephritis. eGFR also naturally declines after age 40. A single low result may need to be confirmed with repeat testing. Your healthcare provider will evaluate the full picture and guide next steps specific to you.

One of the trickiest things about reduced kidney function is that mild to moderate drops in eGFR often cause no symptoms at all — which is why routine testing matters so much. When symptoms do appear, they can include fatigue and weakness, swelling in the ankles, feet, or hands, shortness of breath, nausea, and loss of appetite. You might also notice changes in how often you urinate, the colour of your urine, or a foamy appearance. Itchy skin and high blood pressure are also associated with declining kidney function. Having any of these symptoms does not confirm a kidney problem, and many people with low eGFR feel perfectly fine. Discuss any symptoms alongside your eGFR result with your healthcare provider.

Seeing your eGFR shift between lab visits is common and does not always signal a problem. Short-term factors like dehydration, recent intense exercise, or eating a large high-protein meal before your blood draw can temporarily affect your creatinine level and, in turn, your eGFR calculation. What doctors pay closest attention to is the trend across several tests over time — a gradual, consistent decline is more clinically meaningful than a single fluctuating result. If your eGFR drops significantly or keeps falling across multiple readings, that warrants closer investigation. Bringing your Serumo trend data to your appointments can help your healthcare provider see the full pattern and advise you on what, if anything, needs to be done.