Purpose: This study aimed to investigate sex differences in the effect of body mass index (BMI) and stress on high-risk diabetes mellitus (DM). Methods: Secondary analysis of data from 4,271 male and female adults participating in the Sixth Korea National Health and Nutrition Examination Survey 2015 was performed. The participants were evaluated using questionnaires and blood tests. Data were analyzed using descriptive statistics, t-test, χ2-test, and multiple logistic regression analysis (SPSS 24.0). Results: To identify sexspecific effects, interaction variables were included. Hemoglobin A1c (HbA1c) level was higher in men than in women, and the risk of DM decreased 0.31 times in women compared to that in men. As age increased, the odds of risk DM increased 1.03. The risk of DM increased 1.99 times in overweight individuals and 2.79 times for obese individuals compared to that in individuals with normal weight. Stress levels were higher in women than in men, but stress is not an influential factor in high-risk DM. In age-sex interaction, the odds of risk DM increased 1.02 in women compared to that in men as age increased. Conclusion: HbA1c level was affected by age-sex interaction, and age and sex should be considered in the application of HbA1c in the diagnosis of DM.