# Creatinine and eGFR

Creatinine is a waste product from your muscle's creatine. Your body makes it at a fairly steady rate, and your kidneys clear it (mostly by filtration, with a little tubular secretion). So serum creatinine is a core marker of kidney function. But its raw value depends on your muscle mass, age, sex, meat intake, and creatine supplements. To adjust for that, labs report an estimated glomerular filtration rate (eGFR), using the 2021 race-free CKD-EPI equation as the current standard. A lower eGFR means less filtering capacity. And it is strongly tied to cardiovascular events, frailty, and death.

## Sources

- Levey AS, Stevens LA, Schmid CH, Zhang YL, Castro AF 3rd, Feldman HI, et al.. (2009). A new equation to estimate glomerular filtration rate. Annals of Internal Medicine. https://doi.org/10.7326/0003-4819-150-9-200905050-00006
- Inker LA, Eneanya ND, Coresh J, et al.. (2021). New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa2102953

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_Canonical: https://longevity-switzerland.com/en/glossary/creatinine-egfr · Part of Longevity Cities · Updated 2026-06-22_