We monitored the glucose levels of 3 patients who had undergone total gastrectomy without hypoglycemic symptoms using the Free Style Libre Pro®, a continuous glucose monitoring system, and assessed fluctuations. Mean patient age was 75±3 years and all were men. The highest and lowest sensor glucose (SG) values were 337±54 mg/dL and 44±8 mg/dL, respectively. In 2 of the 3 patients, the lowest SG value was 40 mg/dL, which was the lower limit of detection. After administration of alpha-glucosidase inhibitors, all patients showed improvement in the highest and lowest SG values, and the proportion of time when the SG value was 180 mg/dL or above decreased. The proportion of time when the SG value was less than 70 mg/dL increased in 2 of the 3 patients. However, mean SG values during the same time periods were higher than the pretreatment values, and the proportion of time when the value was less than 60 mg/dL decreased. Consensus error grid analysis performed using blood glucose levels from selfmonitored measurements and meal tolerance tests taken during continuous glucose monitoring versus SG values revealed that all data pairs were within the clinically acceptable regions (zones A and B).