A safety pen needle assembly comprising: a tubular carrier having a distal end, a proximal end and a transverse engagement wall located between said proximal and distal ends, said engagement wall having a proximally-facing outer surface and an aperture formed through said engagement wall, a needle having a distal end, for injection into a patient, and a proximal end for establishing fluid communication with a medical cartridge; a needle hub, said needle being fixed to said needle hub so as to move therewith, said needle hub being disposed in said carrier distally of said engagement wall, and a first biasing means for urging said needle hub from a first hub position where said needle extends through said aperture of said engagement wall to a second hub position where said proximal end of said needle is located distally of said proximally-facing outer surface of said engagement wall; characterised in that said safety pen assembly further comprises a shield for selectively covering said distal end of said needle; a second biasing means for urging said shield from a first shield position where said distal end of said needle is not covered by said shield to a second shield position where said distal end of said needle is covered by such shield; and a locking arrangement that holds said shield in said first shield position that does not cover said distal end of said needle, said locking arrangement including a manual trigger which, upon activation, releases said shield; wherein when said manual trigger is activated while said shield holds said needle hub in said first hub position and said shield is in said first shield position, said shield is released to move to said second shield position under said bias of said second biasing means and said needle hub moves to said second hub position under said bias of said first biasing means. a tubular carrier having a distal end, a proximal end and a transverse engagement wall located between said proximal and distal ends, said engagement wall having a proximally-facing outer surface and an aperture formed through said engagement wall, a needle having a distal end, for injection into a patient, and a proximal end for establishing fluid communication with a medical cartridge; a needle hub, said needle being fixed to said needle hub so as to move therewith, said needle hub being disposed in said carrier distally of said engagement wall, and a first biasing means for urging said needle hub from a first hub position where said needle extends through said aperture of said engagement wall to a second hub position where said proximal end of said needle is located distally of said proximally-facing outer surface of said engagement wall; characterised in that said safety pen assembly further comprises a shield for selectively covering said distal end of said needle; a second biasing means for urging said shield from a first shield position where said distal end of said needle is not covered by said shield to a second shield position where said distal end of said needle is covered by such shield; and a locking arrangement that holds said shield in said first shield position that does not cover said distal end of said needle, said locking arrangement including a manual trigger which, upon activation, releases said shield; wherein when said manual trigger is activated while said shield holds said needle hub in said first hub position and said shield is in said first shield position, said shield is released to move to said second shield position under said bias of said second biasing means and said needle hub moves to said second hub position under said bias of said first biasing means.