<p>The effects of metal exposure on telomere length have attracted considerable attention, but definitive evidence is still lacking in the diabetic population. Thus, this study was conducted to explore the associations of metal mixture with telomere length and the mediated effects of glucose metabolism among the Chinese diabetic population. Eleven metals in serum and relative telomere length of leucocyte were quantified among 1516 diabetic population based on a large-scale diabetic retinopathy screening program in southern China. Multiple statistical models were used to evaluate the single and joint effects of metal mixture on telomere length. Moreover, to assess the mediating roles of glucose metabolism in the associations between metals and telomere length, mediation analyses were performed. In single-exposure models, serum levels of nickel and thallium were identified to be negatively associated with telomere length, while magnesium showed an inverted U-shaped association with telomere length. Consistent findings from three mixed-exposure analyses indicated that increased serum level of metal mixture was associated with decreased telomere length, with nickel playing a major role in the joint effects of the metals. Mediation analyses further revealed that the associations of nickel and metal mixture with telomere length were partially mediated by glycated hemoglobin, and the mediated proportions were 4.26% and 4.38%, respectively. Moreover, the associations between metals exposure and telomere length were observed to be more prominent in males. Our results indicated that exposure to metal mixture was associated with shortened telomere length, which may be partially mediated by glycated hemoglobin.</p>