A communication wake-up scheme for an implantable medical device may involve repeatedly activating a receiver to determine whether an external device is attempting to establish communication with the implantable device. To reduce the amount of power consumed by the implantable device in conjunction with the wake-up scheme, the scheme may involve conducting preliminary RF signal detections as a precursor to conducting a full scan. In this way, power may be conserved since the more power intensive full scans may be performed less frequently. This preliminary detection of RF signals also may be adapted to reduce the number of full scans performed by the implantable device that do not result in communication with the external device. In some embodiments the adaptation involves adjusting one or more thresholds that are used in conjunction with the preliminary detection of RF signals. In some embodiments a wake-up scheme may involve scanning for signals using an initial RF band that is relatively wide, and then scanning for signals using narrower RF bands.