eGFR is a calculated functional biomarker rather than a single molecule. It is derived from serum creatinine measurements combined with age, sex and sometimes other variables using standardized equations (for example, MDRD or CKD‑EPI) to estimate glomerular filtration. Because it is an estimate, values are influenced by factors that affect creatinine production such as muscle mass, diet, and some medications. Historically developed to provide a simple, reproducible index of filtration, eGFR is widely used to track changes in kidney filtering capacity over time. Its core role is to summarize the kidneys’ ability to clear small-molecule waste from the blood, which intersects with fluid balance, toxin removal and the handling of metabolic byproducts relevant to cardiovascular physiology.

Lower eGFR values suggest reduced filtering capacity and are associated with patterns of decreased renal clearance and altered handling of fluids and metabolites; such patterns can affect interpretation of other biomarkers in the panel. Higher-than-expected eGFR values may reflect increased filtration (hyperfiltration) from physiologic or metabolic states, or they can result from low serum creatinine due to low muscle mass or analytical variability. Interpretation should always consider clinical context and the Cardio Zoomer’s other measures, since single eGFR readings can be affected by transient factors like hydration and lab-method differences.

Cardio Zoomer includes eGFR to place renal clearance into the broader cardiovascular and metabolic picture. Knowing estimated filtration helps clinicians interpret lipid, inflammatory, metabolic and drug-response markers, and it clarifies whether altered biomarker levels may be influenced by kidney handling or systemic vascular stress. This adds important context for personalized risk assessment and monitoring.