Embedding a thermoelectric generator (TEG) in a biological body is a promising way to supply electronic power in the long term for an implantable medical device (IMD). It can resolve the service life mismatch between the IMD and its battery. This paper is dedicated to developing a real prototype, which consists of an implanted TEG and a specified boosted circuit. Two implanted TEG modules were constructed and a boosted circuit with a highly integrated DC/DC converter was fabricated to stabilizing the energy output and improving the voltage output for the implanted TEG. According to the experiments, such a device combination was already capable of supporting a clock circuit in the in vivo rabbit whose power consumption is much higher than an ordinary cardiac pacemaker. Meanwhile, a close to reality theoretical model was established for characterizing the implanted TEG. This study is expected to serve as a valuable reference for future designs of the implanted TEG and its boosted circuit.