The estimated glomerular filtration rate (eGFR) expresses kidney filtration function indexed to a standard body surface area of 1.73 m². The CKD-EPI 2021 equation refit the earlier 2009 coefficients without a race term, following a recommendation that race — a social construct — should not adjust laboratory estimates of kidney function. It uses age, sex at birth, and serum creatinine, and applies to adults 18 years and older.
Results are reported alongside the KDIGO GFR categories (G1 through G5). A single eGFR value does not establish chronic kidney disease; chronicity generally requires abnormalities persisting for at least three months, and category G1 or G2 requires an additional marker of kidney damage such as albuminuria.
Creatinine-based estimates carry known limitations. Muscle mass substantially above or below average (bodybuilding, amputation, severe malnutrition, advanced cirrhosis), unusual protein intake, creatine supplements, and drugs that block tubular creatinine secretion (for example trimethoprim or cimetidine) can bias the estimate. In these settings, or when treatment decisions depend on an exact value, confirmatory measurement with cystatin C or a measured clearance is commonly considered.
The equation is not validated for children, pregnancy, or acute kidney injury, where filtration changes faster than creatinine reaches steady state. Values near decision thresholds should be interpreted in the full clinical context, including urinalysis, albuminuria, and trajectory over time.
This summary is informational. It does not provide a diagnosis, staging determination, or treatment recommendation, and it does not replace clinical judgment or current guideline documents.