eGFR (estimated glomerular filtration rate)

An estimate of how well your kidneys filter your blood, calculated from a blood test — higher is better.

What it measures

Estimated filtration rate, computed (not directly measured) from your blood creatinine, age and sex.

Why it matters

It’s the core measure of kidney function and the basis of chronic kidney disease (CKD) staging. Early CKD is silent, so eGFR is often the first sign.

Healthy target

≥ 90 is normal; < 60 for 3+ months defines CKD

How to read your value

It’s an estimate with real error bars — a single reading can be thrown off by hydration, a recent big meat meal, muscle mass or acute illness. CKD needs the drop to persist for at least 3 months, not one low value. Very muscular or very low-muscle people are systematically mis-estimated.

What can affect it

• Age (it declines gradually)
• Muscle mass and recent meat intake
• Hydration and acute illness
• Certain medications; the equation used

Does the target differ by age or sex?

Falls with age as a normal trend. The 2021 CKD-EPI equation removed the old race coefficient (which raised estimates for Black patients and could delay CKD recognition); sex is built into the equation.

When to talk to a clinician

An eGFR under 60, a downward trend, or protein/albumin in the urine should be confirmed over time and assessed by a clinician.