A non-implantable communication unit (100) conducts wireless communication with an implantable medical device, IMD, (200). The communication unit (100) comprises a request processor (120) for generating power down requests destined to the IMD (200) and triggering temporary power down of the IMD radio equipment (220). When the communication unit (100) receives a data packet from the IMD (200) or a connected programmer (300) it determines the size of the data packet. A timer processor (140) sets a timer (152, 154) to a value defined based on the determined size. A processor controller (160) selectively controls the operation of request processor (120) to generate or stop generating the power down requests based on a current value of the timer (152, 154). Power down of the IMD radio equipment (220) is thereby prevented if it is likely that the IMD (200) comprises data to transmit to the communication unit (100) as predicted based on data packet sizes.
