What Is eGFR?
The estimated rate at which your kidneys filter blood.
Medically reviewed by Dr. Rishi Kumar Kafle, MBBS, MD, FASN · Last reviewed June 2026
eGFR (estimated glomerular filtration rate) estimates how much blood your kidneys filter each minute, standardised to 1.73m² of body surface area. It is the standard measure for staging chronic kidney disease.
What the Glomeruli Do
Each kidney holds about a million tiny filters called glomeruli. The glomerular filtration rate is the volume of blood they clear per minute. Because it cannot be measured directly in routine care, it is estimated from a blood test — hence the “e” in eGFR.
Filtering blood is how the kidneys remove waste products and excess fluid while keeping the substances the body needs. As filtration falls, those wastes — including creatinine — build up in the blood, which is precisely why a rising creatinine signals a falling eGFR. The rate is reported as a volume of blood cleared per minute, scaled to a standard body size so that one person’s result can be compared fairly with another’s.
How eGFR Is Calculated
eGFR is derived from your serum creatinine, age, and sex using the race-free CKD-EPI 2021 equation. No urine collection is needed. Some versions add cystatin C for a muscle-independent estimate. Calculate yours with the eGFR calculator.
What the CKD-EPI 2021 Equation Uses
The race-free CKD-EPI 2021 equation turns a single blood test into an estimate of filtration. It needs four inputs: your serum creatinine, your age, your sex, and a fixed normalisation to 1.73m² of body surface area. It does not use a race coefficient, because the 2021 update removed it. Two internal constants tune the result by sex: a creatinine cut-point κ (0.7 for women, 0.9 for men) and an exponent α (−0.241 for women, −0.302 for men). You do not need to do this maths yourself — the equation runs inside the eGFR calculator, and you simply read the result.
Because creatinine rises as filtration falls, a higher creatinine produces a lower eGFR. The equation also applies a small downward adjustment for age, which is why a healthy older adult can have a slightly lower number than a healthy younger one. This is normal and is covered on the eGFR by age page.
How eGFR Maps to Kidney Function
eGFR is reported as a single number in mL/min/1.73m², and that number places you on the standard kidney-function scale. An eGFR of 90 or above usually means normal filtration; a value that stays below 60 for three months or more is the threshold for chronic kidney disease. The same scale is used to divide CKD into stages G1 through G5.
| eGFR | What it indicates |
|---|---|
| ≥ 90 | Normal or high filtration |
| 60–89 | Mildly reduced — often normal without other signs of damage |
| 45–59 | Mild to moderate reduction (stage G3a) |
| 30–44 | Moderate to severe reduction (stage G3b) |
| 15–29 | Severely reduced (stage G4) |
| < 15 | Kidney failure (stage G5) |
One result rarely tells the whole story. A value is interpreted alongside your normal range, your trend over time, and a urine albumin test. See what a low eGFR means for a fuller explanation.
eGFR vs Creatinine Clearance
eGFR is reported per 1.73m² and is used to stage kidney disease, while creatinine clearance is reported in mL/min and is used for drug dosing. They estimate related but distinct quantities and are not interchangeable. eGFR is standardised to an average-sized body, so it is ideal for comparing one person with the population and for staging disease. Creatinine clearance reflects your actual body size, so it is preferred when a drug dose must match your real kidneys. A pharmacist may convert between the two, but for most lab reports the eGFR you receive is the staging number.
Why eGFR Is Estimated, Not Measured
The true filtration rate can be measured directly, but only with a timed urine collection or an injected tracer, which is slow and impractical for routine care. The CKD-EPI equation was built and validated so that a single, widely available blood test gives a close estimate instead. That trade-off — a small loss of precision for a large gain in convenience — is why nearly every lab reports an eGFR rather than a measured one. For an even more muscle-independent estimate, some labs add cystatin C to the calculation.
What Can Affect an eGFR Result
Because eGFR is calculated from creatinine, anything that changes creatinine can shift the estimate. Creatinine comes from muscle, so a very muscular person tends to have a higher creatinine and a slightly lower estimated eGFR, while a person with low muscle mass can have the reverse. A large meat-heavy meal or intense exercise shortly before the blood draw can nudge creatinine up for a short time. Dehydration, a recent illness, and some medicines can also move the number. These are reasons a single result is read with care rather than taken as a fixed verdict.
- Muscle mass — more muscle raises creatinine and can lower the estimate slightly.
- Diet and exercise — a heavy protein meal or hard workout before the test can raise creatinine briefly.
- Hydration and illness — short-term changes can cause a temporary dip that recovers.
- Some medicines — a few drugs affect creatinine or filtration and are taken into account.
For these reasons, an unexpected result is usually repeated, and the pattern over several tests matters more than any single figure. The cystatin C version sidesteps the muscle-mass issue, which is why it is sometimes used to confirm a borderline creatinine-based result.
How to Read Your Own eGFR
When you receive an eGFR on a lab report, three questions are more useful than the single number. First, how does it compare with the normal range for your age? Filtration declines gradually with age, so a value that looks low can be normal in an older adult — see eGFR by age. Second, what is the trend? A stable value over time is reassuring, while a steadily falling one deserves attention. Third, is there albumin in the urine? Pairing eGFR with a urine albumin test gives a fuller risk picture than either alone.
If your result sits below 60, it does not by itself mean kidney disease — the value has to stay below that level for three months or more before it is called chronic kidney disease. To see where your own number falls on the scale, calculate it with the eGFR calculator and read the result against the bands above, then discuss anything unexpected with your clinician rather than acting on one figure alone.