Poor medication adherence is a well-known barrier to meeting therapeutic goals in diabetes mellitus (DM). We aimed to clarify the status of medication adherence and determine clinical variables significantly associated with medication adherence in Japanese patients with DM using a large claims database. Analyzed were data from 7459 patients with DM whose medical records on oral hypoglycemic agents (OHA) were available for at least 1 y (mean age 53 y, HbA1c 7.2%). Medication adherence was evaluated by the proportion of days covered (PDC); PDC <80% was defined as non-adherent. Multivariate logistic regression model was used to identify clinical variables significantly associated with non-adherence. The mean PDC was 80.4%, and 33.1% of patients were non-adherent. The PDC for sulfonylureas, biguanides, thiazolidines, α-glucosidase inhibitors, glinides, and DPP-4 inhibitors were 82% 82%, 79%, 79%, 73%, and 84%, respectively. The PDC for OHA was negatively correlated with HbA1c, LDL cholesterol, and triglycerides. HbA1c decreased by 0.2% with 25% increases in PDC. Logistic analysis indicated that older age and ≥3 concomitant medications were significantly associated with adherence while male sex and smoking were significantly associated with non-adherence (Figure), implying the necessity for effective strategies to improve medication adherence in patients in these categories. Disclosure Y. Yaguchi: None. K. Fujihara: None. T. Osawa: None. M. Yamamoto: None. M. Kaneko: None. M. Kitazawa: None. M. Harada: None. Y. Matsubayashi: None. T. Yamada: None. N. Yamanaka: None. H. Seida: None. H. Sone: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kowa Pharmaceutical Europe Co. Ltd., Kyowa Hakko Kirin Co., Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited.