The present invention relates to a disposable injection device for delivering a dose of medicament, comprising a generally elongated housing (10), a container (14) containing medicament to be injected through a needle (16), force means (34) acting on said container and capable of, upon activation, move said container and said needle for penetration and subsequently expelling medicament through said needle, activating means (26) arranged to activate said force means, characterized in that said activating means comprises a needle shield (12) arranged slidable in relation to said housing, a collapsible holding member (58) connected to the inner end of said needle shield, whereby, upon movement of said needle shield, said collapsible holding member collapses when a certain force is applied by the needle shield, and whereby further movement of said needle shield activates said activation means, which in turn releases said force means initiating an injection of medicament.