Estimate your Glomerular Filtration Rate (eGFR) to check kidney function using the CKD-EPI 2021 equation.
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Estimated Glomerular Filtration Rate (eGFR) measures how efficiently your kidneys filter waste products out of the blood, and it's the primary indicator used worldwide to diagnose and stage chronic kidney disease (CKD). This calculator uses the CKD-EPI 2021 creatinine equation, the version jointly endorsed by the National Kidney Foundation and the American Society of Nephrology (NKF-ASN) task force, which removed the race variable used in the older 2009 version after a review found it produced systematically less accurate results for Black patients. The equation relies only on age, sex, and serum creatinine level, measured through a simple blood test. eGFR naturally declines somewhat with age even in healthy kidneys, and results are grouped into stages G1 through G5, ranging from normal or high kidney function down to kidney failure requiring dialysis or transplant. This tool is for educational purposes only and cannot replace a full clinical evaluation by a physician.
The kidneys' main job is filtering waste and excess fluid out of the bloodstream, and the rate at which they do this — the glomerular filtration rate — is widely considered the single best overall measure of kidney function available. Because directly measuring filtration rate requires an invasive and time-consuming clinical procedure, doctors almost always rely on an estimate calculated from a routine blood test instead, which is what "eGFR" refers to.
This calculator uses the CKD-EPI 2021 equation, developed by the Chronic Kidney Disease Epidemiology Collaboration and adopted as the current standard by the National Kidney Foundation and American Society of Nephrology. It replaced an earlier 2009 version that included a race adjustment; a 2021 task force review concluded that adjustment introduced bias and recommended removing it so that Black and non-Black patients with the same creatinine, age, and sex receive the same eGFR estimate. The equation itself needs only three inputs — age, sex, and serum creatinine — making it something a physician can calculate from bloodwork that's already routinely ordered.
Results are grouped into five CKD stages: G1 (eGFR 90+, normal or high function, though still a concern if kidney damage markers like protein in urine are present), G2 (60–89, mildly reduced), G3a and G3b (45–59 and 30–44, moderately reduced), G4 (15–29, severely reduced), and G5 (below 15, kidney failure, at which point dialysis or transplant is typically discussed). A single low reading doesn't automatically mean CKD — a diagnosis generally requires reduced eGFR, or other evidence of kidney damage, persisting for at least three months.
Several everyday factors can shift a creatinine-based eGFR estimate without reflecting a real change in kidney function: muscle mass (creatinine is a muscle breakdown product, so very muscular or very frail people can get skewed estimates), recent intense exercise, high dietary meat intake, and certain medications. This is why an unusually low or borderline reading is typically followed up with a repeat test rather than acted on immediately.
Because kidney function typically declines gradually and silently over years before symptoms appear, tracking eGFR over time — rather than reacting to one number — is what actually guides clinical decisions. This calculator can tell you which stage a given creatinine value falls into, but staging, monitoring frequency, and any treatment plan should always be determined by a physician with your full medical history.
A lower eGFR generally indicates reduced kidney function, but a single result should always be confirmed and interpreted by a doctor alongside other tests.
The CKD-EPI 2021 equation used here removed the race variable to provide a more equitable and accurate estimate for all patients.
No. It only provides an educational estimate. Diagnosis requires clinical evaluation, repeated lab tests, and a qualified physician.