The commonly used setup of an automatic glucose-clamp is analyzed as a control system. In the analysis, the measuring device and the patient are modeled in a simple but effective way. Strict limits in response time, parasitic oscillation amplitude, and accuracy are defined in order to approach the physician's requirements. A new control algorithm is developed, and the gain coefficients which can lead the system within these limits are defined. Computer simulations with model parameters from the literature (patient) and from experimental data (measuring device) are presented. Preliminary in vivo trials are also presented.