In diabetic practice, continuous glucose monitoring (CGM) has been more used for glucose variability. Authors have reported and developed the clinical study of Low Carbohydrate Diet (LCD) and Calorie Restriction (CR) through Japan LCD Promotion Association (JLCDPA). A diabetic case is presented with normalizing glucose variability by LCD meal checked by CGM. Case is 51 years female with type 2 diabetes mellitus (T2DM). At first visit, HbA1c was 10.0%, glucose was 288mg/dL, BMI 39.1, GOT 16IU/mL, HDL-C 33mg/dL, Triglyceride 152mg/dL. CR meal was provided on day-1 to day-5 and LCD meal with 12% carbohydrate on day-6 to day-13. Average glucose value from CGM was 292mg/dL, 235mg/dL, 160mg/dL, 140mg/dL, 124mg/dL in day 3,5,7,9,11 respectively. On day-13, total Ketone bodies (T-KB) 540μmol/L (-131), Acetoacetic acid (AcAc) 86μmol/L (-55) and 3-hydroxybutyric acid (3-OHBA) 454μmol/L (-85). Weight reduction was 5kg on day-14 and 11.2kg on day-70 with BMI 34.6. Thus, LCD showed a remarkable glucose-lowering effect in short term. FreeStyle Libre (Abbott, USA) seems to be a useful apparatus for monitoring the detailed fluctuation of blood glucose. These results would become fundamental and reference data and contribute to the LCD research development in the future.