The present invention relates to a medicament delivery device comprising a housing (10), which housing is arranged to accommodate a medicament container (20) a power unit (88) comprising: a drive force element (98), an actuation unit (90, 102) operably connected to said drive force element (98) which actuation unit (90, 102) is movable, upon activation of said drive force element (98), for expelling a dose of medicament from said medicament container (20) a monitoring unit (130) provided with an electrical power source (140) for operating said monitoring unit (130). The invention is characterised in that the medicament delivery device further comprises an activation element (160) operably connected to said actuation unit (90, 102), to said monitoring unit (130) and to said electrical power source (140), wherein said activation element (160) is arranged to allow connection between said electrical power source (140) and said monitoring unit (130) when said actuation unit (98, 102) is moved.
