An infusion system is for infusing a fluid into the body of a patient. The infusion system includes at least one sensor for monitoring blood glucose concentration of the patient and an infusion device for delivering fluid to the patient. The sensor produces at least one sensor signal input. The infusion device uses the at least one sensor signal input and a derivative predicted algorithm to determine future blood glucose levels. The infusion device delivers fluid to the patient when future blood glucose levels are in a patient's target range. The infusion device is capable of suspending and resuming fluid delivery based on future blood glucose levels and a patient's low shutoff threshold. The infusion device suspends fluid delivery when future blood glucose levels falls below the low shutoff threshold. The infusion device resumes fluid delivery when a future blood glucose level is above the low shutoff threshold.