An infusion pump system providing therapy to a patient in a closed-loop or semi-closed loop mode can safely automatically revert to open-loop therapy. The system stores a default open-loop basal rate profile in memory. The system also continually tracks the insulin on board for the patient over a plurality of closed-loop therapy intervals. When an error or event occurs requiring reversion to open-loop therapy, the system automatically provides therapy according to the open-loop basal rate profile and the tracked insulin on board amount.
