A glucose management system comprising: a sensor configured to be positioned subcutaneously in a user; a drug delivery device configured to exchange data with the sensor and programmed to deliver a user-initiated insulin bolus to the user; and a controller configured to exchange data with the drug delivery device, the controller comprising: a user interface, and a processor coupled to the user interface and configured to calculate a user-initiated insulin bolus, wherein the processor is programmed to: determine whether the user has input data into the user interface pertaining to a blood glucose concentration value, BG, as measured by the glucose management system, calculate a blood glucose correction component of the user-initiated insulin bolus based on the blood glucose concentration value, determine whether the user has input data into the user interface pertaining to a carbohydrate value, CHO, and calculate a meal component of the user-initiated insulin bolus based on the carbohydrate value, determine a system-facing insulin-on-board value based on the at least one of the components of the user-initiated insulin bolus, wherein a predetermined percentage of a total user-initiated insulin bolus is attributed to the system-facing insulin-on-board when the blood glucose concentration value and the carbohydrate value are not input into the controller and the continuous glucose measurement value is not available. a sensor configured to be positioned subcutaneously in a user; a drug delivery device configured to exchange data with the sensor and programmed to deliver a user-initiated insulin bolus to the user; and a controller configured to exchange data with the drug delivery device, the controller comprising: a user interface, and a processor coupled to the user interface and configured to calculate a user-initiated insulin bolus, wherein the processor is programmed to: determine whether the user has input data into the user interface pertaining to a blood glucose concentration value, BG, as measured by the glucose management system, calculate a blood glucose correction component of the user-initiated insulin bolus based on the blood glucose concentration value, determine whether the user has input data into the user interface pertaining to a carbohydrate value, CHO, and calculate a meal component of the user-initiated insulin bolus based on the carbohydrate value, determine a system-facing insulin-on-board value based on the at least one of the components of the user-initiated insulin bolus, a user interface, and a processor coupled to the user interface and configured to calculate a user-initiated insulin bolus, wherein the processor is programmed to: determine whether the user has input data into the user interface pertaining to a blood glucose concentration value, BG, as measured by the glucose management system, calculate a blood glucose correction component of the user-initiated insulin bolus based on the blood glucose concentration value, determine whether the user has input data into the user interface pertaining to a carbohydrate value, CHO, and calculate a meal component of the user-initiated insulin bolus based on the carbohydrate value, determine a system-facing insulin-on-board value based on the at least one of the components of the user-initiated insulin bolus, determine whether the user has input data into the user interface pertaining to a blood glucose concentration value, BG, as measured by the glucose management system, calculate a blood glucose correction component of the user-initiated insulin bolus based on the blood glucose concentration value, determine whether the user has input data into the user interface pertaining to a carbohydrate value, CHO, and calculate a meal component of the user-initiated insulin bolus based on the carbohydrate value, determine a system-facing insulin-on-board value based on the at least one of the components of the user-initiated insulin bolus, wherein a predetermined percentage of a total user-initiated insulin bolus is attributed to the system-facing insulin-on-board when the blood glucose concentration value and the carbohydrate value are not input into the controller and the continuous glucose measurement value is not available.