This book presents a comprehensive study covering the design and application of microwave sensors for glucose concentration detection, with a special focus on glucose concentration tracking in watery and biological solutions. This book is based on the idea that changes in the glucose concentration provoke variations in the dielectric permittivity of the medium. Sensors whose electrical response is sensitive to the dielectric permittivity of the surrounding media should be able to perform as glucose concentration trackers. At first, this book offers an in-depth study of the dielectric permittivity of water-glucose solutions at concentrations relevant for diabetes purposes; in turn, it presents guidelines for designing suitable microwave resonators, which are then tested in both water-glucose solutions and multi-component human blood plasma solutions for their detection ability and sensitivities. Finally, a portable version is developed and tested on a large number of individuals in a real clinical scenario. All in all, the book reports on a comprehensive study on glucose monitoring devices based on microwave sensors. It covers in depth the theoretical background, provides extensive design guidelines to maximize sensitivity, and validates a portable device for applications in clinical settings.