eGFR

The basics

Estimated glomerular filtration rate (eGFR) is a calculation, not a direct measurement, of how much blood your kidneys filter each minute. This panel estimates it from cystatin C, a small protein that the body’s cells produce at a steady rate and the kidneys clear, using the CKD-EPI cystatin C equation. Because cystatin C is largely independent of muscle mass, it can give a more reliable estimate than creatinine, particularly in people with very high or very low muscle mass.

Why this marker matters

eGFR is the workhorse marker of kidney function. Because chronic kidney disease usually progresses silently - without symptoms until late - eGFR is one of the few ways to catch a problem early. A persistent decline below 60 mL/min/1.73 m² over more than three months meets the formal criterion for chronic kidney disease, and warrants a closer look.

Where the typical ranges sit

≥ 90 mL/min/1.73 m² normal; 60–89 mildly decreased; < 60 indicates kidney disease if persistent.

KDIGO categories: G1 ≥ 90 normal or high; G2 60–89 mildly decreased; G3a 45–59 mildly to moderately decreased; G3b 30–44 moderately to severely decreased; G4 15–29 severely decreased; G5 < 15 kidney failure. Mild decreases in older adults can be physiological rather than disease.

Reference ranges differ between laboratories and guidelines. Your CHIRAYOU report uses the range reported by the analysing laboratory, and your interpretation should be discussed with a physician.

Common influencers

• Age (kidney function declines gradually with age)
• Hydration status (acute dehydration can transiently lower eGFR)
• Thyroid function (cystatin C rises in overactive and falls in underactive thyroid)
• Systemic corticosteroids (can raise cystatin C independent of kidney function)
• Diabetes and high blood pressure (the two leading causes of CKD)
• Smoking, obesity, and inflammation (can modestly raise cystatin C)

If your value is outside the range

A first abnormal eGFR should be confirmed with a repeat in a few weeks, ideally combined with a urine albumin/creatinine ratio. Persistent reduction below 60 - and any single result below 45 - should be reviewed with a physician. Modifiable factors like blood pressure control matter substantially for long-term kidney health.

Where this comes from

• KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease
• Inker L. A. et al. - Estimating Glomerular Filtration Rate from Serum Creatinine and Cystatin C (New England Journal of Medicine, 2012) - the source of the CKD-EPI cystatin C equation
• Inker L. A. et al. - New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race (New England Journal of Medicine, 2021)