A computer-controlled regulation for the glucose in the metabolic system is achieved, and fourth-order digital model, obtained from the state differential equations representing the system metabolism. The sample time is chosen sufficiently large to suit the slow metabolic system. A long time delay, imposed by the autoanalyser used for the monitoring and continuous measurement of the glucose concentration, is introduced. A digital proportional-integral-derivative controller is proposed to control the metabolic system and to obtain a zero steady-state error for the closed-loop dynamics. The controller is shown to be robust, using the bounding polynomials suggested by Kharitonov's stability criterion. A family of well-behaved responses are obtained, together with their corresponding internal states. Pole placement is used to optimize the parameters of the controller and to achieve the main goal of controlling the glucoregulatory system.