A system and method for continuous glucose monitoring (CGM) of blood in a blood vessel of a patient using a non-invasive sensor composed of a patch antenna operating in the Industrial, Scientific and Medical (ISM) Radio band (5.725 GHz-5.875 GHz). The device determines the blood glucose concentration of the blood in the blood vessel based on the measured shift of the resonant frequency of the non-invasive antenna patch sensor. A radio frequency (RF) synthesizer is used to drive the patch antenna with a fraction of its output coupled to both the antenna and receiver through a directional coupler. In this approach both the transmitted (FWD) and received (REV) power are processed, by demodulating logarithmic amplifiers, which convert the RF signals to corresponding voltages for downstream processing. The resulting voltages are then fed into a microcontroller and the measured shift in resonant frequency is converted to a real-time glucose concentration.