OBJECTIVES: The Morisky Medication Adherence Scale (MMAS) provides a unique perspective on adherence because of its patient-reported nature.  However, as it is not a condition-specific instrument, evidence of its reliability and validity within the population of interest must be obtained. This study examined the psychometric properties of the recently developed eight-item MMAS (MMAS-8) among those with type 2 diabetes (T2D) using insulin. METHODS: Data from the US 2012 National Health and Wellness Survey (NHWS) were used (N=71,141).  Only respondents who reported a diagnosis of T2D, were currently using an insulin (any type), and reported their last value of HbA1c were included (n=1,198).  Among this subsample, the reliability and validity of the MMAS-8 (when asked only about diabetes medications) were examined using both classic test theory and item response theory (IRT) analyses. RESULTS: A total of 61.44% of respondents were male and the mean age was 60.65 (standard deviation = 10.74). Engagement of non-adherent behaviors (the individual items of the MMAS-8) varied considerably from “stopping medication when feeling worse” (5.76%) to “having difficulty remembering to take all your medications” (32.22%). Internal consistency was adequate (Cronbach’s α=0.68), though would have been improved upon removal of the “did you take your medicine yesterday” item (α=0.70 if removed). One factor was retained using exploratory factor analysis (eigenvalue=1.80). In IRT analyses, most items exhibited solid psychometric properties (e.g., discrimination > 1.40); however, “did you take your medicine yesterday”, provided little information (discrimination=0.20; information=0.02). Overall, the MMAS-8 functioned best when distinguishing among those with above average non-adherence (Θ>0). CONCLUSIONS: These results suggest the MMAS-8 is a reliable and valid instrument to use to assess non-adherence, though certain items are less useful than others for this population. Despite its generic nature, the MMAS-8 should be considered as an adherence measurement tool among those with T2D using insulin.