A blood sugar regulation system including: a blood sugar sensor; an insulin injection device; and a processing and control unit predicting the future evolution of the blood sugar based on a physiological model and accordingly controlling the insulin injection device, wherein the processing and control unit is capable of: a) implementing a calibration of the model by taking into account a history of the measured blood sugar; b) at the end of the calibration step, determining whether the model is satisfactory or not based on at least one numerical indicator representative of the error between the blood sugar estimated based on the model and the real blood sugar measured by the sensor; and c) if the quality of the model is not satisfactory, controlling the insulin injection device without taking into account the predictions made from the model.