What is eGFR and Why Does It Matter?

Estimated Glomerular Filtration Rate (eGFR) is the best available test to measure how well your kidneys are working. It estimates how much blood your kidneys filter every minute, normalized to a standard body surface area of 1.73 m².

What Do Your Kidneys Actually Do?

Your kidneys are powerful filters. Every day, they clean about 180 liters of blood, removing waste products like creatinine and urea, balancing electrolytes, and regulating blood pressure. When kidney function declines, these toxins build up in the body.

How Is eGFR Calculated?

eGFR is calculated from a simple blood test that measures serum creatinine—a waste product from muscle metabolism. The most widely used formula today is the CKD-EPI 2021 race-free equation, which adjusts for age, sex, and creatinine level.

If you have your latest lab report, you can calculate your eGFR instantly using our free calculator.

What Is a Normal eGFR?

• ≥90 mL/min/1.73m²: Normal kidney function (Stage 1 if other kidney damage markers are present)
• 60–89: Mildly decreased (Stage 2)
• 30–59: Moderately decreased (Stage 3)
• 15–29: Severely decreased (Stage 4)
• <15: Kidney failure (Stage 5)

Why eGFR Matters

Early kidney disease often has no symptoms. A declining eGFR can catch problems years before you feel unwell. It also guides medication dosing, tells doctors when to refer you to a nephrologist, and helps track whether treatments are working.

Factors That Can Affect eGFR

• Age: eGFR naturally declines slightly with age.
• Muscle mass: Very muscular people may have higher creatinine and slightly lower eGFR without kidney disease.
• Diet: A very high-meat meal can temporarily raise creatinine.
• Dehydration: Can spike creatinine and lower eGFR.
• Pregnancy: eGFR rises during normal pregnancy.

When to See a Doctor

If your eGFR is below 60 for more than three months, or if you have protein in your urine alongside any eGFR reading, speak to a healthcare provider. Persistent abnormalities warrant further investigation.