eGFR (Estimated Glomerular Filtration Rate)

What it is

eGFR estimates the filtration capacity of the kidneys, expressed in mL/min per 1.73 m² body surface area. Calculated from serum creatinine (and/or cystatin C), age, and sex using the CKD-EPI 2021 equation (which removes the race coefficient used historically).

Reference ranges

• ≥90: normal.
• 60–89: mildly reduced (G2).
• 45–59: mild-moderate CKD (G3a).
• 30–44: moderate-severe (G3b).
• 15–29: severe (G4).
• <15: kidney failure (G5).

Why it matters for longevity

• Kidney function declines ~1 mL/min/year after age 40 in average adults.
• The rate of decline matters more than a single value.
• Reduced eGFR is an independent cardiovascular risk factor.
• Many longevity-relevant drug doses must be adjusted for kidney function.

Cystatin C: the better marker

Creatinine is a muscle-derived molecule; eGFR-creatinine underestimates GFR in muscular individuals and overestimates it in low-muscle adults. Cystatin C is produced more uniformly and gives more accurate eGFR estimates in those edge cases. eGFR-cystatin C also predicts mortality better.

What slows decline

• Tight blood pressure control.
• Avoidance of nephrotoxins (NSAIDs, contrast dye when avoidable, certain antibiotics).
• SGLT2 inhibitors in diabetic and non-diabetic CKD.
• ACE inhibitors / ARBs (when proteinuric).
• Adequate hydration; avoid extremes of protein intake.

Related entries

Chronic kidney disease, Blood pressure, SGLT2 inhibitors.