To evaluate the influence of renal function on oxidative stress, we assessed the distribution of MDA and SOD across three cystatin C-based estimated glomerular filtration rate (eGFRcystC) categories: ≥90 mL/min/1.73 m2 (normal renal function), 60–89 mL/min/1.73 m2 (mild dysfunction), and <60 mL/min/1.73 m2 (chronic kidney disease). Here, CST3 is linked to chronic kidney disease.