Blood glucose diagnostic systems are a world-wide success story. Nevertheless, all the painless solutions available are too expensive to be disposable. We aim to bridge this gap by developing a painless disposable diabetes diagnostic patch. Our envisaged device is fully integrated and autonomous. It harvests the required energy from the environment and features sensor auto-calibration in real-time. In this paper, we present the design and preliminary results of the different parts in the patch including an electrochemical glucose sensor, an enzymatic biofuel cell, and a wireless instrumentation electronics all designed and implemented on the printed circuit board (PCB) technology.