A safety pen needle (1) comprising: a main body (2), a cannula (3) fixed to the main body (2) and at least partially projecting out of the main body (2), a lock element (4) placed inside the main body (2), a thrust element (5) placed inside the main body (2), a shield (6) movable relative to the main body (2) while remaining at least partially inserted within the main body (2). The pen needle (1) is configured to move from a first configuration, in which the shield (6) entirely cover an upper end (32) of the cannula (3), to a second configuration, in which the upper end (32) of the cannula (3) is exposed, due to the action of an external thrust. The pen needle (1) is configured to move from the second configuration to an irreversible third configuration, in which the shield (6) entirely covers the upper end (32) of the cannula (3), due to the action of the thrust exerted by the thrust element (5).
