A pre-filled injection device for apportioning set doses of a liquid drug comprising: A pen-shaped housing extending in a longitudinal direction and having a needle supporting distal end, A removable protective cap mountable on the housing and covering at least a part of the needle supporting distal end between injections, and which removable protective cap is rotatable relatively to the housing when mounted there upon, A non-replaceable cartridge permanently embedded in the housing of the pre-filled injection device and having an interior containing the liquid drug, A needle assembly comprising a needle cannula secured in a hub which needle cannula has a distal end with a distal tip and a proximal end and wherein the proximal end of the needle cannula is inserted into the cartridge, A telescopically movable shield movable from an extended position covering at least the distal tip of the needle cannula to a retracted position and which telescopically movable shield carries a cleaning chamber for cleaning at least the distal tip of the needle cannula between subsequent injections, and which telescopically movable shield is rotatable mounted relatively to the housing, characterised in that the cleaning chamber contains an amount of the same liquid drug as contained in the cartridge, wherein the removable protecting cap when mounted engages the telescopically movable shield such that rotation of the protective cap relatively to the housing is transformed to a rotation of the telescopically movable shield, and wherein the telescopically movable shield is arranged such that the rotation of the telescopically movable shield moves the telescopically movable shield in the proximal direction to a position in which the distal tip of the needle cannula is located in front of the cleaning chamber carried by the telescopically movable shield. A pen-shaped housing extending in a longitudinal direction and having a needle supporting distal end, A removable protective cap mountable on the housing and covering at least a part of the needle supporting distal end between injections, and which removable protective cap is rotatable relatively to the housing when mounted there upon, A non-replaceable cartridge permanently embedded in the housing of the pre-filled injection device and having an interior containing the liquid drug, A needle assembly comprising a needle cannula secured in a hub which needle cannula has a distal end with a distal tip and a proximal end and wherein the proximal end of the needle cannula is inserted into the cartridge, A telescopically movable shield movable from an extended position covering at least the distal tip of the needle cannula to a retracted position and which telescopically movable shield carries a cleaning chamber for cleaning at least the distal tip of the needle cannula between subsequent injections, and which telescopically movable shield is rotatable mounted relatively to the housing, characterised in that the cleaning chamber contains an amount of the same liquid drug as contained in the cartridge, wherein the removable protecting cap when mounted engages the telescopically movable shield such that rotation of the protective cap relatively to the housing is transformed to a rotation of the telescopically movable shield, and wherein the telescopically movable shield is arranged such that the rotation of the telescopically movable shield moves the telescopically movable shield in the proximal direction to a position in which the distal tip of the needle cannula is located in front of the cleaning chamber carried by the telescopically movable shield.