An auto-injector, comprising: an injection assembly, having an upper housing including therein a plunger, a movable piston coupled to the plunger for movement therewith and an actuation button configured to act upon the plunger; a retraction assembly coupled to the injection assembly, the retraction assembly comprising an opaque section and a transparent or translucent section having a portion disposed within the opaque section; an injectable drug container, having a proximal end and a distal end having an outer diameter (OB SB); an end-of-dose visual indicator; wherein the auto-injector operates in a pre-injection stage, an injection stage, and a post-injection, needle retraction stage, and characterised in that, the end-of-dose visual indicator is disposed within the retraction assembly and is configured as a hollow cylinder having an inner diameter (ID IV) that fits against an outer diameter (OB SB) of the distal end of the drug container when the drug container moves distally forward to engage the end-of-dose visual indicator and the end-of-dose visual indicator moves in concert with the drug container from within the opaque section of the retraction assembly into the transparent or translucent section of the retraction assembly upon completion of administration of the drug solution or medicine contained within the drug container and retraction of the drug container during the post-injection, needle retraction stage; wherein, the fit between the inner diameter (ID IV) of the hollow cylinder and the outer diameter (OD SB) of the drug container substantially prevents the hollow cylinder from moving into the transparent or translucent section of the retraction assembly during the pre-injection stage drug container and allows the outer diameter (OB SB) of the drug container to enter into the inner diameter (ID IV) of the hollow cylinder during the injection stage. an injection assembly, having an upper housing including therein a plunger, a movable piston coupled to the plunger for movement therewith and an actuation button configured to act upon the plunger; a retraction assembly coupled to the injection assembly, the retraction assembly comprising an opaque section and a transparent or translucent section having a portion disposed within the opaque section; an injectable drug container, having a proximal end and a distal end having an outer diameter (OB SB); an end-of-dose visual indicator; wherein the auto-injector operates in a pre-injection stage, an injection stage, and a post-injection, needle retraction stage, and characterised in that, the end-of-dose visual indicator is disposed within the retraction assembly and is configured as a hollow cylinder having an inner diameter (ID IV) that fits against an outer diameter (OB SB) of the distal end of the drug container when the drug container moves distally forward to engage the end-of-dose visual indicator and the end-of-dose visual indicator moves in concert with the drug container from within the opaque section of the retraction assembly into the transparent or translucent section of the retraction assembly upon completion of administration of the drug solution or medicine contained within the drug container and retraction of the drug container during the post-injection, needle retraction stage; wherein, the fit between the inner diameter (ID IV) of the hollow cylinder and the outer diameter (OD SB) of the drug container substantially prevents the hollow cylinder from moving into the transparent or translucent section of the retraction assembly during the pre-injection stage drug container and allows the outer diameter (OB SB) of the drug container to enter into the inner diameter (ID IV) of the hollow cylinder during the injection stage.