Presented is a computational system for predicting the blood glucose level to which a diabetic patient is being forced based solely on continuous glucose monitor (CGM) data that then allows optimum and safe calculation of a stabilizing dose to be applied by an insulin pump. This invention hence operates as part of a closed loop insulin delivery system. Included are recursive filters for estimating forthcoming blood glucose levels in real-time. Designed to match typically observed human blood glucose rates of change due to food digestion and insulin injection, these filters are two and three term exponential functions respectively. Such filters are applied to low pass filtered CGM data before being iteratively matched to the raw CGM data in order to yield greater confidence in the recursive predictions. All filters also have infinite response curves with monotonically decreasing amplitudes over time. The recursive and iterative process repeats with the arrival of further CGM measurements, allowing on-going calculation and delivery of optimum and safe insulin by an infusion pump in a close loop insulin delivery system.