Inclusion Criteria:  Patients over 19 years of age Preoperative diabetes history Patients who underwent subtotal or total pancreatectomy Patients who were diagnosed with diabetes mellitus in the evaluation of endocrine function test on the 7th day after pancreaticoduodenectomy, central pancreatectomy, or distal pancreatectomy  Exclusion Criteria:  Patients who have used continuous blood glucose measurement device more than once before. Elderly patients who are not accustomed to using the smartphone applications Serious systemic diseases that can affect diabetes (chronic kidney disease, heart failure, decompensated liver cirrhosis, etc.) Steroid user during the study period Major medical or psychiatric condition that will affect response to treatment