In the present study we examined the efficacy of sodium-glucose cotransporter 2 inhibitors on improvement of glycated hemoglobin (HbA1c) in comparison with the renal threshold for glucose reabsorption in patients with type 2 diabetes mellitus. Patients visited the hospital once a month for a regular follow-up examination with the determination of blood glucose and HbA1c levels, and urinary glucose concentration from spot urine samples. Patient samples were compared before and after ipragliflozin administration. We defined the renal threshold for glucose reabsorption as the lowest blood glucose level that correlated with the first detectable appearance of urine glucose. These data showed a significant negative correlation between improvement of HbA1c level and renal threshold for glucose reabsorption in patients treated with the sodium-glucose cotransporter 2 inhibitor. These findings show that patients who have a higher renal threshold for glucose reabsorption can be expected to more effectively respond to sodium-glucose cotransporter 2 inhibitor therapy in terms of lowering HbA1c levels.