Background: Diabetes has been great problem worldwide. Continuous Glucose Monitoring (CGM) has been in focus, and useful CGM, FreeStyle Libre (Abbott) has been introduced to clinical ordinary practice of medicine. Case and results: The patient was 57 year-old female with type 1 diabetes mellitus (T1DM), who showed BMI 20.6 kg/m2, HbA1c 8.6%. She was on CGM measured glucose every 15 minutes in 24 hours for 14 days. Treatment included 3 times of Insulin Aspart and once of Insulin Glargin. She showed characteristic pattern of blood glucose profile according to the working schedule of the day. Discussion and conclusion: The beneficial points of FreeStyle Libre have been convenient and accurate for clinical use for reducing hypoglycemia episodes. Treatment using CGM associated with multiple daily insulin injection (MDI) confers similar or greater benefits for glycemic profile. When evening insulin was not injected one day, blood glucose increased 320 mg/dL, suggesting 64 g of carbohydrate ingested for supposed calculation. These results suggest that CGM could recommend the timing and doses of insulin injection according to the lifestyle of the patients with clinical merit.