IntroductionThis study aimed to evaluate the impacts of dapagliflozin on 24-hour glucose variability and diabetes-related biochemical variables in Japanese patients with type 2 diabetes who had received basal insulin supported oral therapy (BOT).Research design and methodsChanges in mean daily blood glucose level before and after 48–72 hours of add-on or no add-on of dapagliflozin (primary end point) and diabetes-related biochemical variables and major safety variables during the 12 weeks (secondary end point) were evaluated in the multicenter, randomized, two-arm, open-label, parallel-group comparison study.ResultsAmong 36 participants, 18 were included in the no add-on group and 18 were included in the dapagliflozin add-on group. Age, gender, and body mass index were comparable between the groups. There were no changes in continuous glucose monitoring metrics in the no add-on group. In the dapagliflozin add-on group, mean glucose (183–156 mg/dL, p=0.001), maximum glucose (300–253, p<0.01), and SD glucose (57–45, p<0.05) decreased. Time in range increased (p<0.05), while time above the range decreased in the dapagliflozin add-on group but not in the no add-on group. After 12-week treatment with dapagliflozin add-on, 8-hydroxy-2’-deoxyguanosine (8OHdG), as well as hemoglobin A1c (HbA1c), decreased.ConclusionsThis study showed that the mean daily blood glucose and other daily glucose profiles were amended after 48–72 hours of dapagliflozin add-on in Japanese patients with type 2 diabetes who received BOT. The diabetes-related biochemical variables such as HbA1c and urinary 8OHdG were also obtained during the 12 weeks of dapagliflozin add-on without major adverse events. A preferable 24-hour glucose profile in ‘time in ranges’ and an improvement in reactive oxygen species by dapagliflozin warrant us to evaluate these benefits in larger clinical studies.Trial registration numberUMIN000019457.