A skin insertion mechanism of a needle fixedly positioned in a needle holder (3) with connective means to an injection or analysis system has a skin attachment plate (2) coated with an adhesive layer and a spacer mechanism (4) keeping in the ready-to-use position the skin attachment plate (2) spaced away from the needle support covering the needle. Subcutaneous insertion of the needle is effected by attachment with the adhesive layer to the skin and releasing the spacer mechanism (4) by applying a pre-set trigger point pressure against the skin.