A pen needle to be connected to a container or pen with which a vial of medicament is associated, said needle (1) comprising: - a metal cannula (5) provided with two points (25, 26), one at each end, one known as the patient point (25), and one known as the vial point (26)； - a needle carrier (3), to be connected to said pen； - a container (2), the purpose of which is to receive the entire pen needle (1) prior to use； - a cover element (6), connected to the needle carrier (3) and positioned about the cannula (5)； - a protector element (20), movable within the cover element (6) and arranged to emerge from this latter so as to cover and protect the patient point (25) of the cannula after its extraction from the patient on termination of the injection； - an elastic element (36) arranged to press on the protector element (20) such as to enable it to move on termination of the injection in order to cover the first point (25) of the cannula (5)； - locking means (47) are provided for the elastic element (36) to prevent its action on the protector element (20), at least until a moment subsequent to the commencement of introduction of the cannula (5) into the epidermis, said locking means (47) being removable after the moment in which this introduction commenced.
