Aims/Introduction: To investigate the national trend in the prescription of first-line non-insulin antidiabetic agents and total medical costs (TMCs) after prescribing the drug in Japanese patients with type 2 diabetes.

Materials and Methods: Using the National Database of Health Insurance Claims and Specific Health Check-ups of Japan covering almost the entire Japanese population, we calculated the proportion of each antidiabetic drug from 2014 to 2017, and determined the factors associated with drug selection. The TMCs in the first year after starting the drugs were calculated, and factors associated with the costs were also determined.

Results: Among 1,136,723 new users of antidiabetic agents, dipeptidyl peptidase-4 inhibitors were the most prescribed (65.1%), followed by biguanides (15.9%) and sodium–glucose cotransporter 2 inhibitors (7.6%). Sodium–glucose cotransporter 2 inhibitor and biguanide use increased during 2014–2017 (2.2%–11.4% and 13.7%–17.2%, respectively), whereas the others decreased. Biguanides were not prescribed at all in 38.2% of non-Japan Diabetes Society-certified facilities. The TMCs were the lowest among those who started with biguanides. Fiscal year, age, sex, facility, number of beds and comorbidities were associated with drug choice and TMCs. There were wide regional variations in the drug choice, but not in the TMCs.

Conclusions: Unlike in the USA and Europe, dipeptidyl peptidase-4 inhibitor is the most prescribed first-line medication for type 2 diabetes patients in Japan, while there is a wide variation in the drug choice by facility-type and prefecture.