A needle insertion and retraction mechanism for a drug delivery device having a base to be adhered to a surface, comprising: a source of continuous motion including a tensioned rotator rotatable about an axis thereof, the rotator being tensioned by a tensioned element connected with the rotator and the tensioned element being configured to unwind said rotator about the axis thereof; a user-operated control for said motion source, said control comprising a button and a lever extending at a predetermined angle below the base of the drug delivery device to prevent motion of the button and displaceable from said predetermined angle by the surface, thereby releasing said button; an interrupter to stop rotation of said tensioned rotator at a predetermined location, thereby dividing said rotation into a first motion part and a second motion part, said second motion part being in angular continuity with said first motion part; a motion translation mechanism comprising a cam connecting said tensioned rotator to an injection needle, wherein: when the lever is displaced from said predetermined angle by the surface and the button is depressed said motion translation mechanism translates rotation of the tensioned rotator into an insertion motion of the injection needle to extend said injection needle during said first motion part, and said interrupter stops the rotation of the rotator at the predetermined location and when the lever is thereafter removed from the surface, the interrupter is released and the rotation of the rotator is continued, permitting said motion translation mechanism to translate the continued rotation of the tensioned rotator into a retraction motion of the injection needle to retract said injection needle during said second motion part. a source of continuous motion including a tensioned rotator rotatable about an axis thereof, the rotator being tensioned by a tensioned element connected with the rotator and the tensioned element being configured to unwind said rotator about the axis thereof; a user-operated control for said motion source, said control comprising a button and a lever extending at a predetermined angle below the base of the drug delivery device to prevent motion of the button and displaceable from said predetermined angle by the surface, thereby releasing said button; an interrupter to stop rotation of said tensioned rotator at a predetermined location, thereby dividing said rotation into a first motion part and a second motion part, said second motion part being in angular continuity with said first motion part; a motion translation mechanism comprising a cam connecting said tensioned rotator to an injection needle, wherein: when the lever is displaced from said predetermined angle by the surface and the button is depressed said motion translation mechanism translates rotation of the tensioned rotator into an insertion motion of the injection needle to extend said injection needle during said first motion part, and said interrupter stops the rotation of the rotator at the predetermined location and when the lever is thereafter removed from the surface, the interrupter is released and the rotation of the rotator is continued, permitting said motion translation mechanism to translate the continued rotation of the tensioned rotator into a retraction motion of the injection needle to retract said injection needle during said second motion part. when the lever is displaced from said predetermined angle by the surface and the button is depressed said motion translation mechanism translates rotation of the tensioned rotator into an insertion motion of the injection needle to extend said injection needle during said first motion part, and said interrupter stops the rotation of the rotator at the predetermined location and when the lever is thereafter removed from the surface, the interrupter is released and the rotation of the rotator is continued, permitting said motion translation mechanism to translate the continued rotation of the tensioned rotator into a retraction motion of the injection needle to retract said injection needle during said second motion part.