Diabetes has been a crucial medical and social problem worldwide. For adequate nutritional therapy, there have been discussions concerning Calorie Restriction (CR) and Low Carbohydrate Diet (LCD). We have investigated glucose variability of diabetic patients applying CR, LCD, continuous glucose monitoring (CGM) and applied FreeStyle Libre which is flash glucose monitoring (FGM). The patient is a 40-year-old female with type 2 diabetes mellitus (T2DM), who showed BMI 20.7, postprandial blood glucose 257 mg/dL. HbA1c 12.1%, Glycoalbumin 31.6% (11.6-16.4), serum C-peptide 2.0 ng/ml and unremarkable data of liver function, renal, lipids. She was provided the intervention of three stages, which are i) CR with 60% carbohydrate in Day 1-2, ii) LCD meal with 12% carbohydrate in Day 3-5; iii) LCD + Sodium-glucose cotransporter 2 (SGLT2) inhibitor (Ipragliflozin L-Proline 50mg) in Day 6-12. The glucose profile was measured by FreeStyle Libre Pro (Abbott) for 14 days. The daily profile of blood glucose was abruptly decreased on Day 6. Time percentage of satisfactory blood glucose 70-180 mg/dL (/24h) was 0%, 0%, 2%, 14%, 0%, 54%, 100% in Day 1-7, respectively. These results suppose the acute clinical efficacy of SGLT2 inhibitor, and this report would become a reference for future diabetic practice and research.