〔Abstract〕 Objective To assess the association between Life eight(LE8) scores and diabetes mellitus(DM), and to examine the mediating effect of Methylmalonic acid(MMA). Methods Based on cross-sectional data from the 2011—2014 National Health and Nutrition Examination Survey(NHANES), weighted multivariable logistic regression analyses were conducted to assess the association between the LE8 score and DM. A mediation model was further constructed to evaluate the mediating effect of MMA. Results The weighted multivariable logistic regression analysis showed a significant negative correlation between LE8 score and the risk of DM. After adjusting for potential confounders, a 1-point increase in LE8 was associated with a 7% reduction in DM risk(OR=0.93, 95%CI: 0.92-0.93, P=0.000 1). In contrast, the level of circulating MMA did not show a statistically significant relationship with DM risk(OR=0.99, 95%CI: 0.89-1.10, P=0.886 8). Further subgroup analysis by age revealed that in participants under 60 years of age, circulating MMA levels were positively associated with DM risk(OR=1.39, 95%CI: 1.19-1.62, P