eGFR – Reference Ranges, Indicators & Result Interpretation

eGFR — the estimated glomerular filtration rate — is a key marker used to assess kidney function and the kidneys' ability to filter blood. Reference values for eGFR vary by age, sex, and race, and accurate interpretation is critical in diagnosing kidney disease. Understanding these results is essential for early detection and monitoring of chronic kidney disease, allowing for timely therapeutic intervention and improved patient quality of life.

How to interpret your results

Your eGFR (estimated glomerular filtration rate) is reported as a single number in mL/min/1.73 m² — roughly the volume of blood your kidneys filter each minute, scaled to a standard body surface area. A result above 90 generally means your kidneys are filtering normally, and a value below this may indicate chronic kidney disease (CKD).

Because true GFR can only be obtained from a complex clearance study, the number on your report is an estimate calculated from a formula, and imprecision is inherent in every eGFR equation. Clinicians look at trends across multiple tests using the same equation, and pair the eGFR with a urine albumin-to-creatinine ratio (uACR) to get a fuller picture of kidney health.

CKD stages by eGFR

The NHS stages chronic kidney disease using five eGFR bands:

Stages G1 and G2 require evidence of kidney damage from other tests (such as protein in the urine) to count as CKD — a normal eGFR alone is not diagnostic.

eGFR normal range by age and sex

A healthy adult eGFR is generally above 90 mL/min/1.73 m². Both US and UK guidance use 90 as the upper-end anchor for healthy kidney function, and 60 as the threshold below which sustained values define chronic kidney disease.

The 2021 CKD-EPI creatinine equation already accounts for age and sex alongside serum creatinine. Because muscle mass — which produces the creatinine the equation measures — varies between men and women, and because creatinine production also varies by body size and activity, the equation incorporates your demographic information before producing a number. The eGFR on your report has already been age- and sex-corrected, so you do not need to re-interpret it against a separate scale.

Why the number changes over time

What clinicians watch for is the rate of change. A noticeable drop between tests, or a number that crosses below 60 and stays there, warrants follow-up. The NIDDK recommends comparing values calculated with the same equation — if your lab switched equations between two tests, some of the apparent change may simply reflect the formula change rather than your kidneys.

Body size, diet, and activity level can all influence creatinine and therefore the eGFR derived from it. Small fluctuations between tests are expected, and a single borderline result is typically rechecked rather than acted on immediately. A full assessment usually combines repeat eGFRs, a creatinine trend, and a urine ACR result.

What a low eGFR means (and what may cause it)

A low eGFR suggests your kidneys may not be filtering blood as efficiently as they should, and a very low result may indicate kidney failure. The most common cause of a sustained low value is chronic kidney disease, which is why eGFR is used as a screening test in routine bloodwork rather than waiting for symptoms.

Common contributors to a low result

• Diabetes and high blood pressure — the two conditions most often linked to declining kidney function
• Cardiovascular disease, including coronary artery disease and heart failure
• A family history of kidney disease, diabetes, or inherited kidney conditions
• Long-term medications that can affect the kidneys, such as lithium, omeprazole, or NSAIDs
• Recent acute kidney injury — sudden kidney damage that may or may not fully recover
• Urinary blockages or frequent urinary tract infections
• Obesity (BMI greater than 25)

A single low number is not the same as chronic kidney disease. Because creatinine — and therefore the calculated eGFR — depends on body size, diet, and activity level, transient factors can shift a single result. Providers usually repeat the test before assigning a CKD stage, and compare the result to a creatinine trend and a urine ACR to separate a one-off dip from real kidney injury.

What a high eGFR means

A high eGFR — well above the normal-range anchor of 90 — usually reflects healthy filtration. But MedlinePlus is explicit that the test isn’t perfect, and an abnormal result is possible even without kidney damage. That works both ways: a high number doesn’t rule out kidney problems, and a low number doesn’t guarantee them.

Two main factors can push a result up artificially. First, the 2021 CKD-EPI creatinine-only equation slightly overestimates kidney function in non-Black individuals — on average by about 4%. Second, creatinine is influenced by muscle mass and diet, so people with low muscle mass produce less creatinine, which mathematically yields a higher eGFR than their true kidney function warrants.

For that reason, an eGFR well above 90 is almost never acted on alone. If there is any clinical concern — such as protein in the urine or risk factors for kidney disease — providers typically request additional tests, including a urine ACR or a cystatin C-based eGFR. The NIDDK specifically recommends the combined creatinine-cystatin C equation when an eGFR sits close to a clinical decision threshold.

How eGFR is calculated (CKD-EPI, creatinine, cystatin C)

The current US standard for adults is the 2021 CKD-EPI creatinine equation (2021 CKD-EPI eGFRcr), recommended by the NIDDK and the National Kidney Foundation–American Society of Nephrology Task Force. Two related 2021 CKD-EPI equations are also available: a combined creatinine-cystatin C equation, and a cystatin C-only equation.

A key change from older formulas is that the 2021 CKD-EPI equations do not include a race coefficient. The earlier 2009 race-based CKD-EPI equation used a Black/non-Black variable; the 2021 versions calculate eGFR from creatinine (or cystatin C), age, and sex alone.

Inputs to the calculation

Your provider’s lab plugs the following into the equation:

• Serum creatinine (or serum cystatin C, or both) from your blood draw
• Your age
• Your sex
• For some pediatric and combined equations, height and weight

Creatinine is a waste product from normal muscle breakdown — healthy kidneys filter it out, and when filtration drops, creatinine builds up in the blood. Cystatin C is a small protein produced by most cells, and unlike creatinine it is not meaningfully affected by muscle mass, age, or diet.

When cystatin C is added, and known limits

The NIDDK considers the combined creatinine-cystatin C equation more accurate than creatinine alone, especially when the eGFR is close to a decision threshold — for example with drug dosing or kidney transplant evaluation. Cleveland Clinic notes cystatin C is often added when a creatinine result is inconclusive, when the patient is over 65, or when muscle mass is unusually high or low. The NIDDK is also explicit that no single eGFR equation is best for every patient.

eGFR vs other kidney tests (creatinine, BUN, uACR, cystatin C)

eGFR is the centerpiece of a kidney workup, but it is rarely interpreted alone. Each companion test answers a different question.

The NHS pairs eGFR with the urine ACR to stage kidney disease, reporting ACR in three bands — A1 (less than 3 mg/mmol), A2 (3 to 30 mg/mmol), and A3 (more than 30 mg/mmol) — where a higher band indicates more albumin leak. The NIDDK recommends using urine albumin and the albumin-to-creatinine ratio in anyone with or at risk for kidney disease.

eGFR is also routinely included in standard bloodwork. Cleveland Clinic notes it is often part of the basic metabolic panel ordered at routine checkups, which is why most adults already have one on record without specifically asking.

When to talk to your doctor

eGFR is most useful as a trend, but specific results and symptoms warrant prompt follow-up. Talk to your clinician if any of the following apply:

• Your eGFR is below 60 mL/min/1.73 m² on a single test, so a repeat can confirm whether it is sustained
• Your eGFR has dropped noticeably between two recent tests, even if both values are in the normal range
• You have swelling in your legs, feet, ankles, hands, or face
• You are urinating more or less often than usual, particularly waking at night to urinate
• You see blood in your urine
• You have persistent fatigue, muscle cramps, nausea or vomiting, or loss of appetite
• You have dry, itchy skin without another obvious cause
• You have unintended weight loss alongside any abnormal kidney result
• You are taking a long-term medication that can affect the kidneys — lithium, omeprazole, or NSAIDs — and have not had an eGFR checked recently

If you have already been diagnosed with chronic kidney disease, your provider will set a personalized schedule for repeat testing using the same equation, because comparing eGFRs from different formulas can make a change look bigger or smaller than it is.

Frequently asked questions

What does eGFR mean in a blood test?

eGFR stands for estimated glomerular filtration rate — a calculated estimate of how much blood your kidneys filter each minute, derived from your creatinine level, age, and sex. It is the standard screening test for chronic kidney disease, usually reported automatically whenever creatinine is measured.

What is a normal eGFR?

For most adults, an eGFR above 90 mL/min/1.73 m² is considered a healthy result. Values between 60 and 89 with other signs of damage suggest early disease, and a value below 60 may indicate chronic kidney disease.

What does a low eGFR mean?

A low eGFR suggests your kidneys may not be filtering well, and a very low result may point to kidney failure. Common contributors include diabetes, high blood pressure, cardiovascular disease, and certain long-term medications. A single low result is normally rechecked before any conclusion is drawn.

What does a high eGFR mean?

A high eGFR usually reflects healthy filtration, but MedlinePlus notes an abnormal result is possible even without kidney damage. The 2021 CKD-EPI creatinine equation slightly overestimates filtration in non-Black individuals by about 4% on average, and low muscle mass or diet can also push the number up artificially.

Why doesn’t the 2021 CKD-EPI equation use race?

The NIDDK now recommends the 2021 CKD-EPI equations, which calculate eGFR from creatinine (or cystatin C), age, and sex — without a race coefficient. The earlier 2009 CKD-EPI equation included a Black/non-Black variable that the 2021 versions remove.

Why is cystatin C sometimes added to eGFR?

Creatinine depends on muscle mass, age, and diet, so people at the extremes of those variables can have a misleading creatinine-based eGFR. Cystatin C is not affected by those factors, and the NIDDK considers the combined creatinine-cystatin C equation more accurate, especially near clinical decision thresholds.

Is eGFR included in a metabolic panel?

Yes — eGFR is routinely calculated and reported whenever serum creatinine is measured, including as part of the basic or comprehensive metabolic panel. The NIDDK recommends labs report eGFR every time creatinine is measured.

Do I need to fast for an eGFR test?

Sometimes. Cleveland Clinic notes the creatinine measurement is sensitive, and preparation may include fasting, avoiding meat for a day or two before the test, and holding certain medications. Eating meat beforehand can transiently raise creatinine and skew the result.

References

• MedlinePlus (U.S. National Library of Medicine, NIH)
• Cleveland Clinic
• NHS
• NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases, NIH)

Last reviewed: 2026-05-17