Recently, the interest in implantable antennas has significantly increased because of their attractive and diverse medical applications. As the human body is a hostile environment for implantable antennas, where it absorbs most of the antenna’s radiation, designing implantable antennas has become a challenging task. Despite the many efforts that have been made to construct successful designs of robust performance against the complicated human body environment; more efforts are still needed to overcome the current challenges. This paper aims to review recent advances in designing implantable antennas and upcoming research progress in the area of implantable antennas. To achieve this aim, the main differences in performance between antennas in free space and lossy media are emphasized firstly. Then, the main antenna’s designs proposed for implantable applications are surveyed and categorized based on critical design parameters. Finally, the main characteristics of existing designs are summarized, and future needs are highlighted.