Background: The efficacy of administering a sodium-glucose cotransporter 2 inhibitor during insulin therapy has not been established. In this study, we examined its effects based on diurnal glycemic patterns using continuous glucose monitoring (CGM).
Methods: The subjects were 15 patients who had received insulin therapy for 1 year or more. A CGM device was attached to all subjects for 1 week. The administration of canagliflozin at 100 mg was started 4 days after attachment. The mean blood glucose level, standard deviation (SD), mean amplitude of glycemic excursions (MAGE), mean of daily difference of blood glucose (MODD), and area under the curve (AUC)(>180, <70) after the start of administration were compared with the pretreatment values. In addition, we compared changes in the unit number of insulin between basal and bolus insulin. Furthermore, we investigated the influence of canagliflozin on oxidative stress markers and cytokines using 8-hydroxy-2’-deoxyguanosine (8-OHdG), tumor necrosis factor- (TNF-), and adiponectin as parameters.
 Results: The mean blood glucose level decreased from 161.1 to 139.1 mg/dL (P<0.01). The SD decreased from 36.5 to 29.6 mg/dL (P=0.05). The MAGE decreased from 89.2 to 77.4 mg/dL (P<0.01), and the MODD decreased from 34.3 to 25.5 mg/dL (P<0.05). All parameters showed significant improvements in diurnal changes. AUC of >180, it decreased from 339.1 to 113.6 mg/dL(P<0.05). AUC of <70, it slightly decreased from 1.6 to 0.3 mg/dL (P=0.08). 
The total unit number of basal insulin decreased from 128 to 76, and that of bolus insulin decreased from 266 to 154; the dose of insulin could be markedly decreased.
In addition, the mean 8-OHdG level decreased from 11.4 to 10.8 ng/mgCre (P<0.05), and the mean TNF- level decreased from 2.31 to 1.79 pg/mL (P=0.10). The mean adiponectin level increased from 5.01 to 5.53 g/mL(P<0.05).
Conclusion: Canagliflozin improved blood glucose changes in type 2 diabetes using insulin. In addition, the results suggest its antioxidant actions.

Efficacy of additional canagliflozin administration to type 2 diabetes receiving insulin therapy