in the form of a modular skin mountable drug delivery device 1 comprising a patch unit 2 and a pump unit 5 as the pump unit comprises a reservoir it may also be termed a reservoir unit when supplied to the user each of the units are preferably enclosed in its own sealed package not shown the embodiment shown in fig1 comprises a patch unit provided with an insertable transcutaneous device e g needle cannula or sensor in case an actual embodiment requires the patch unit to be mounted on the skin and the transcutaneous device inserted before a pump or other unit can be attached it follows that the method of use would be adopted correspondingly the patch unit comprises a flexible patch portion 10 with a lower adhesive mounting surface 12 adapted for application to the skin of a user and a housing portion 20 in which a transcutaneous device not shown is arranged the transcutaneous device comprises a pointed distal end adapted to penetrate the skin of a user and is adapted to be arranged in fluid communication with the pump unit in the shown embodiment the pointed end of the transcutaneous device is moveable between an initial position in which the pointed end is retracted relative to the mounting surface and an extended position in which the pointed end projects relative to the mounting surface the transcutaneous device may also be moveable between the extended position in which the distal end projects relative to the mounting surface and a retracted position in which the distal end is retracted relative to the mounting surface the.