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OBJECTIVE To use the framework of the Health Belief Model (HBM) to explore factors associated with metformin use among adults with prediabetes. RESEARCH DESIGN AND METHODS We analyzed survey data from 200 metformin users and 1,277 nonmetformin users with prediabetes identified from a large, insured workforce. All subjects were offered the National Diabetes Prevention Program (DPP) at no out-of-pocket cost. We constructed bivariate and multivariate models to investigate how perceived threat, perceived benefits, self-efficacy, and cues to action impacted metformin use and how demographic, clinical, sociopsychological, and structural variables impacted the associations. RESULTS Adults with prediabetes who used metformin were younger and more likely to be women and to have worse self-rated health and higher BMIs than those with prediabetes who did not use metformin. Those who used metformin were also more likely to be aware of their prediabetes and to have a personal history of gestational diabetes mellitus or a family history of diabetes. After consideration of perceived threat, perceived benefits, self-efficacy, and cues to action, the only independent predictors of metformin use were younger age, female sex, higher BMI, and cues to action, most specifically, a doctor offering metformin therapy. CONCLUSIONS Demographic and clinical factors and cues to action impact the likelihood of metformin use for diabetes prevention. Perceived threat, perceived benefits, and self-efficacy were not independently associated with metformin use. These results highlight the importance of patient-centered primary care and shared decision-making in diabetes prevention. Clinicians should proactively offer metformin to patients with prediabetes to facilitate effective diabetes prevention.