Content Validity of a Questionnaire Based on the Theory of Planned Behavior to Assess the Psychosocial Determinants of Insulin Adherence

•Although adherence to drug treatment in type 2 diabetes mellitus reduces disease complications, nonadherence to insulin has been reported by outpatients.•The study provides a theory-based measure with content validity evidence, aimed at assessing the psychosocial determinants of adherence to insulin therapy behavior in people with type 2 diabetes mellitus.•Identifying the psychosocial determinants of insulin adherence therapy will enable health providers in delivering tailored theory-based interventions to promote insulin adherence.