On-body injection device

An on-body injection device comprising:

• a housing provided with a medicament inlet;
• a movable member channel arranged in the housing;
• a movable member arranged in the movable member channel, the movable member channel having a fluid inlet in fluid communication with the medicament inlet and a fluid outlet, wherein the movable member is configured to move in the movable member channel, by a built-up overpressure inside the movable member channel relative to a pressure on the movable member outside the movable member channel, from a first movable member position in which the movable member blocks the fluid outlet to a second movable member position in which the fluid outlet is in fluid connection with the fluid inlet;
• a skin penetration device configured to move from a starting position to a skin penetration position;
• a conduit connected to the skin penetration device and to the fluid outlet;
• and
• a movable structure pretensioned in a direction away from the movable member,
• wherein the movable member is configured to engage with the structure when the movable member is in the first movable member position, preventing the structure from moving away from the movable member, and
• wherein the movable member is configured to disengage from the structure when the movable member is moved towards the second movable member position, causing the pretensioned structure to move away from the movable member to an intermediate position, bringing the skin penetration device from the starting position to the skin penetration position.