OBJECTIVES: This study aimed to assess patients’ medication adherence associated with changes in dosing regimen (monotherapy (MONO), dual therapy (DUAL), and fixed-dose combination therapy (FDCT)) in type 2 diabetics. METHODS: This study utilized a retrospective cohort of Medicaid enrollees from eight states with type 2 diabetes newly starting antidiabetic therapy. Patients were followed for 12 months after initiation of index dosing regimen (MONO, DUAL, or FDCT) and 12 months after early change in dosing regimen (DUAL or FDCT). Demographic characteristics and pharmacy records were extracted for eligible patients. Prescription refill patterns were used to calculate Medication Possession Ratio (MPR). To compare changes in adherence before and after a change in the dosing regimen, Pre- and Post-index MPR were calculated. Differences in MPR and demographics between groups were analyzed using T-tests and ANOVA for continuous variables and chi-squared tests for categorical variables. RESULTS: There were 10,749 patients in the study cohort including 8,528 (79.4%) MONO, 1,558 (14.5%) DUAL, and 663 (6.2%) FDCT patients. No significant different in distribution of age was found across the three groups. Among the 1318 patients who changed their therapy, 809 (61.4%) had an augmentation to DUAL and 509 (38.6%) switched to FDCT. Mean MPR for the entire cohort was 0.81. ANOVA indicated that medication adherence rates were significantly different across MONO, DUAL, and FDCT dosing regimens (p <0.001). Patients on dual therapy had significantly higher MPR rate (0.91) as compared to patients on the other regimens. Patients switching to FDCT had significantly lower pre-index MPR than patients augmenting to dual therapy (p-value <0.01). Patients switching to FDCT also had significantly lower post-index MPR than the augmentation patients (p-value <0.001). CONCLUSIONS: Patients, health care providers like physicians, pharmacists, and Medicaid programs can collaborate together to devise strategies to improve patient medication adherence and other outcomes.