Ultra-wideband (UWB) technology has been considered for the physical layer in recently proposed IEEE 802.15 standard (TG6) for wireless body area networks. Wireless links covered by this standard will operate in UWB unlicensed band with antennas on implanted devices having small form factors. Except for those installed on-body and on external receivers, the antenna will be operating in-body, surrounded by body tissue. Body tissues have high dielectric constants and are highly dissipative. Once implanted beneath multiple layers of tissue, the device, which is expected to be consuming very low power, experience heavy losses in its transmission and reception path. Therefore, it is essential that antenna losses, both mismatch and resistive, are minimised. In this paper we will demonstrate a method to minimize antenna mismatch losses by loading the antenna with insulating material.