Tight glycemic control is important to mitigate diabetes complications but is difficult to achieve because of the increased risk of hypoglycemia. With the recent advances in the management of type 1 diabetes (T1D), the use of continuous glucose monitors and sensor-augmented pumps have benefited both the patients with T1D and their caregivers. This chapter presents the current state of predictive low glucose suspend (PLGS) systems and their clinical use in various clinical trials and real-world settings. The primary goal of these algorithms is to prevent or reduce hypoglycemia and to decrease the burden of diabetes care. The systems use a continuous glucose monitor that communicates with an algorithm that suspends insulin delivery based on the current glucose level and rate of change, with slightly different rules for the resumption of insulin delivery. The use of most of these systems was associated with a reduction in hypoglycemic events without consequent hyperglycemia. With the development of automated insulin delivery systems, the PLGS algorithm was built into the hybrid closed-loop controllers that adjust basal rate delivery and/or correct hyperglycemia to improve hemoglobin A1c.
