Estimated Glomerular Filtration Rate

Your eGFR is a calculated estimate, worked out by a formula from your creatinine (a waste product your muscles make), your age, and your sex, not a filtration rate measured directly. It estimates how many milliliters of blood your kidneys filter each minute. Above 90 is normal, and the number that matters is 60: an eGFR under 60 that lasts more than 3 months is what points to chronic kidney disease.

What is eGFR, and what does it measure?

eGFR (estimated glomerular filtration rate) estimates your glomerular filtration rate: the volume of blood your kidneys' filters, the glomeruli, clean per minute. A healthy pair of kidneys filters roughly 90 to 120 milliliters a minute. ¹ You cannot measure that directly without a specialized test, so a lab calculates it from your serum creatinine, a muscle waste product cleared almost entirely by the kidneys, adjusted for your age and sex.

Because creatinine is the raw input, eGFR inherits creatinine's blind spot. Creatinine rises only once filtration has already fallen a fair way, so the estimate built on it can read reassuringly normal while filtering capacity is quietly dropping.

That is the case for reading eGFR rather than creatinine alone: the equation adjusts a raw waste level for the fact that a 25-year-old weightlifter and a frail 80-year-old make very different amounts of creatinine at the same true kidney function. If you have your creatinine, age, and sex, you can see roughly where your own eGFR lands.

What is a normal eGFR?

For most adults a normal eGFR is 90 or above, though it falls slowly with age even in healthy kidneys, so plenty of well people in their 70s sit in the 60s or 70s. Many labs report high results as a capped range (often above 60, or above 90) rather than a precise figure, because the estimate is too rough at the top of the range to trust a single high number. The full staging runs from G1 down to G5.

These G-stage cutoffs are set by the KDIGO CKD guideline, the international standard used by US labs. ¹ Two things the stages hide: G2 (60 to 89) on its own, with no protein leaking into the urine, is usually not disease, only kidneys filtering a little more slowly; and a single number in any stage is a snapshot, not a trend.

What does a low eGFR mean?

A low eGFR means your kidneys are estimated to be filtering more slowly than expected for your age and sex. Below 60 is the threshold that gets attention, because that is where the filtering reserve healthy kidneys carry starts to run thin. What it does not tell you is why, or whether the drop is lasting. Dehydration, a recent infection, or a new medication can all push the number down for days without any permanent change to the kidneys, and a large meat meal or hard exercise can nudge it for a few hours.

When does a low eGFR mean kidney disease?

One eGFR under 60 is a flag, not a diagnosis. Chronic kidney disease is defined by persistence: the abnormality has to still be there after more than 3 months, which is why a clinician repeats the test rather than acting on a single result.

abnormalities of kidney structure or function, present for >3 months, with implications for healthKDIGO 2024 CKD Guideline, definition of chronic kidney disease

So a value of, say, 54 on one Tuesday means: recheck it, and look for damage the filtering number can miss. A slow slide across the 60 line over years reads very differently from a one-off dip during a stomach bug. ¹

Why one eGFR is not the whole kidney picture

eGFR captures only how fast the kidneys filter. It says nothing about whether the filters are leaking, and damaged filters often leak protein into the urine long before the filtering speed drops. That second signal is caught by a urine albumin-to-creatinine ratio (ACR), a test that measures how much albumin (a blood protein) is escaping into your urine. Filtration and damage are the two axes a kidney assessment measures at once.

For how the two axes combine into a single risk picture, and what else sits on a standard kidney panel, see how to read a kidney function test. When a creatinine-based eGFR does not seem to fit the person, a cystatin C test, a second filtration marker that muscle mass does not distort, is used to confirm or correct it. ⁴

Why did my eGFR change when race was removed from the equation?

Until 2021, the standard US eGFR equation (CKD-EPI) multiplied the result by about 1.16 for anyone recorded as Black, a coefficient with no biological basis that raised their estimated filtration. ⁵ The 2021 refit dropped race entirely. ² For Black adults, the same creatinine now returns a lower eGFR than before, which moved some people into a more advanced CKD stage overnight, not because their kidneys changed but because the old math had been inflating the number.

The change was recommended by a joint National Kidney Foundation and American Society of Nephrology task force, which called for labs to adopt the race-free equation right away and to use cystatin C more widely to confirm results. ³

How much can you trust the number?

eGFR is an estimate, and estimates have error bars. The 2021 CKD-EPI equations land within 30 percent of a directly measured filtration rate about 86 to 90 percent of the time. ² Flipped around, the number is off by more than 30 percent in something like 1 in 7 to 1 in 10 people, and the estimate is loosest exactly where you most want precision: near the normal range, in the 60s to 90s.

That imprecision is the practical reason a borderline eGFR is confirmed rather than trusted outright, with a repeat test, a urine ACR, and sometimes a cystatin C, before anyone attaches the label chronic kidney disease.

How is eGFR tested, and how often?

You do not order eGFR on its own. It is calculated automatically whenever a lab measures your serum creatinine, which sits on the basic metabolic panel and comprehensive metabolic panel, the routine blood panels ordered at most checkups. No fasting is required for creatinine itself, though it often rides along with fasting tests like glucose and lipids. There is no separate charge: if your creatinine is measured, your eGFR is reported.

How often to retest depends on why the number matters:

• No risk factors and a normal eGFR: it comes with routine bloodwork, so most adults get it at general checkups without a special schedule.
• Diabetes, high blood pressure, heart disease, or a family history of kidney failure: these are the groups guidelines flag for regular kidney checks, typically at least yearly, with both eGFR and a urine ACR. ¹
• A first low or borderline eGFR: expect a repeat within about 3 months to see whether it persists, which is what separates a temporary dip from chronic kidney disease.

Can eGFR improve?

It depends on the cause. If a low reading came from something temporary, dehydration, an acute illness, or a drug that nudges the number, eGFR often recovers on the repeat test once the trigger is gone. A slow decline from long-standing diabetes or high blood pressure is usually not reversed, but its pace can be slowed a lot by treating those drivers, which is a conversation for your clinician rather than a supplement aisle. No pill, cleanse, or tea reliably raises eGFR, and anything marketed that way is worth treating with suspicion.

If your eGFR ever drops quickly, or a low value comes with swelling, much less urine than usual, or new nausea and confusion, that is a same-week medical question to raise now.

Read as a whole, your eGFR is one estimate on a filtering scale: a single number that means most when it is paired with a urine ACR, repeated before it is trusted, and seen next to your creatinine, your blood pressure, and the rest of your history.