The invention relates to a safety needle assembly for injecting a fluid into a human body comprising a cylindrical housing (1,40,103+104) with a bottom surface (9,50) supporting a needle cannula (30,130) and a shield telescopically (2,43,102) movable relative to the housing. A spring (25,125) located within the housing urges the shield in a distal needle covering direction and a locking member also provided inside the housing moves simultaneously with the shield during injection and automatically locks the shield in a position where the sharp end of the needle cannula is concealed thereby irreversible immobilizing the safety needle assembly.
