Background <p>Advanced glycation end products, particularly pentosidine, are implicated in age-related diseases and are influenced by renal function and glycemic status. Although elevated pentosidine levels are well documented in individuals with chronic kidney disease (CKD) stage G3b or higher, their association with early reductions in estimated glomerular filtration rate (eGFR), including in individuals with preserved renal function, remains incompletely understood.</p> Methods <p>We conducted a cross-sectional analysis of 813 Japanese adults from the Fukuoka Epidemiological Study of Atherosclerosis who underwent routine health checkups. Serum pentosidine and Nε-(carboxymethyl)lysine (CML) levels were measured and analyzed in relation to eGFR categories and glycemic markers.</p> Results <p>Serum pentosidine levels were significantly associated with early reductions in eGFR, even among individuals with values including individuals with preserved renal function (P for trend &lt; 0.01), whereas serum CML levels remained largely unchanged. In multivariable logistic regression analysis, lower eGFR category was significantly associated with elevated serum pentosidine levels (odds ratio, 1.94; 95% confidence interval, 1.40–2.70) after adjustment for covariates. In contrast, no significant association was observed between HbA1c-defined glycemic status and serum pentosidine levels. Triglycerides, high-sensitivity C-reactive protein (hs-CRP), and obesity (body mass index ≥ 25&#xa0;kg/m²) were inversely associated with serum pentosidine levels.</p> Conclusions <p>Lower eGFR, including in individuals with preserved renal function, was associated with higher serum pentosidine levels in this general population. These findings suggest that subtle reductions in renal function, even in individuals with preserved renal function, are associated with higher serum pentosidine levels, which may reflect a combination of cumulative oxidative stress and altered renal handling.</p>