A closed loop/semi-closed loop infusion system provides therapy modification and safeguards against the over-delivery or under-delivery of insulin. A glucose sensor system is configured to obtain a measured blood glucose value. A controller is operationally connected with the glucose sensor system and configured to trigger an alarm based on a measured blood glucose value or amount of insulin delivered, selectively perform calibration of the glucose sensor system when the alarm is triggered, and adjust a therapy delivery parameter when the alarm is triggered, wherein the adjusted therapy delivery parameter is limited to be within a boundary. Thereafter, a delivery system delivers therapy at the adjusted therapy delivery parameter.