Abstract: A drug delivery system comprising drug expelling means and electronic circuitry with a sensor system adapted to determine an expelled amount of drug, the sensor system comprising a switch for actuating the sensor system between an off and on state. The electronic circuitry is adapted to actuate the sensor system from a high-power on-state to a low-power sleep state after a given amount of time to save energy, and, with the sensor system in the low-power sleep state, detect when the switch is actuated from the on-state to the off-state, this creating an error period. When an error period has been detected a display indicates to the user that the sensor system has been in an error state for a period of time corresponding at least to the error period.

Abstract: The present invention relates to a wireless data communication module (100) for a drug injection device. The wireless data communication module (100) comprises a folded flexible carrier member (107) comprising a plurality of stacked component support regions (203, 205, 207, 209, 211) and a display (103), such as a LCD or OLED display, electrically connected to a first component support region (203) of the folded flexible carrier member (107) via a first set of electrical connection terminals. The display (103) comprises an outwardly facing readable display and an opposing, downwardly facing, optical reflector (319). The wireless data communication module (100) additionally comprises a NFC antenna (105) attached to a second component support region (205) of the folded flexible carrier member (107) situated below the first component mounting region (203). The optical reflector (319) of the display comprises an optically reflective and non-magnetically permeable material.