A pen needle assembly comprising: a hub having a distal end and a proximal end; a needle fixed to said hub, said needle having a distal end, formed for insertion into a patient, and a proximal end; an inner shield disposed proximally of said hub, said inner shield including a mounting assembly configured to cooperatively engage a pen injector body; a spring disposed between said inner shield and said hub configured to bias said hub distally; an outer shield having a distal end and a proximal end and a tubular body at least partially encircling a portion of said needle; said outer shield having at least portions located radially outward further from said needle than said inner shield such that said outer shield at least partially encases said hub, said needle, said inner shield, and said spring; and a releasable retaining means configured to releasably retain said hub in a first locked state against said biasing of said spring; and wherein, said distal end of said needle is covered by said outer shield with said hub being in the first locked state, wherein, upon release of said releasable retaining means, said hub moves under force of said spring to a second unlocked state, and, wherein, in said second unlocked state, said distal end of said needle extends distally from said distal end of said outer shield, said pen needle being so designed that a predetermined extent of proximal movement of said outer shield relative to said inner shield causes deflectable latches formed on said hub and being part of said releasable retaining means to deflect inwardly with respect to a shoulder on the outer shield to disengage said shoulder and to release said hub. a hub having a distal end and a proximal end; a needle fixed to said hub, said needle having a distal end, formed for insertion into a patient, and a proximal end; an inner shield disposed proximally of said hub, said inner shield including a mounting assembly configured to cooperatively engage a pen injector body; a spring disposed between said inner shield and said hub configured to bias said hub distally; an outer shield having a distal end and a proximal end and a tubular body at least partially encircling a portion of said needle; said outer shield having at least portions located radially outward further from said needle than said inner shield such that said outer shield at least partially encases said hub, said needle, said inner shield, and said spring; and a releasable retaining means configured to releasably retain said hub in a first locked state against said biasing of said spring; and wherein, said distal end of said needle is covered by said outer shield with said hub being in the first locked state, wherein, upon release of said releasable retaining means, said hub moves under force of said spring to a second unlocked state, and, wherein, in said second unlocked state, said distal end of said needle extends distally from said distal end of said outer shield, said pen needle being so designed that a predetermined extent of proximal movement of said outer shield relative to said inner shield causes deflectable latches formed on said hub and being part of said releasable retaining means to deflect inwardly with respect to a shoulder on the outer shield to disengage said shoulder and to release said hub.