OBJECTIVES: Schizophrenia has been found to be associated with poor medication compliance, and a higher prevalence of diabetes. Once a hypoglycemic therapy is started, appropriate compliance to the therapy is crucial for good glycemic control. This study aimed to compare hypoglycemic therapy medication compliance, and health care costs after the initiation of the therapy, between type II diabetics with schizophrenia versus those without schizophrenia. METHODS: This study used the claims database of the National Health Insurance program. Enrollees who began oral hypoglycemic therapy in 2001-2002 (the index date), and had been diagnosed with schizophrenia and refilled at least one prescription of antipsychotic(s) in the year prior to the index date were included in the study (the case group). Enrollees without schizophrenia who began oral hypoglycemic therapy in 2001-2002 were selected from a randomly selected sample of the enrollees (the comparison group). Good medication compliance was defined as an medication possession ratio (MPR)≥0.8. Ordered logistic models were adopted to assess associations between factors with medication compliance. RESULTS: There were 1196 and 3188 subjects in the case group and comparison group, respectively. Forty-one percent of the case group and 30% of the comparison group were good compliant. The cost of hypoglycemic therapy was significantly higher in the case group, while the total diabetes-related cost was not significantly different between the two groups. The regression results indicated that comorbid schizophrenia was correlated with a higher likelihood of good compliance. In a subgroup analysis of diabetics with schizophrenia, good compliance to antipsychotics in the previous year was significantly associated with a greater probability of being better compliant with hypoglycemic therapy. CONCLUSIONS: Diabetics with schizophrenia, compared with those without such a condition, were more compliant in their hypoglycemic therapy, and had higher cost of hypoglycemic therapy in the first year of the therapy.