This invention relates to a method and a device for predicting the glucose concentration of a subject and recommending therapeutic action. The responses of the user's glucose to administered doses of insulin, dietary carbohydrates, and other factors influencing glucose concentration are measured individually for a given user. Once these responses are learned as a function of time, the method and device can receive information about the factors that have been recently or will soon be administered and can recommend which other factors should also be administered.