Disclosed is a method for manufacturing a cannula unit with a cannula housing and a cannula, in which a cannula is injection molded onto a molding core pin having an outer diameter d1 to produce a cannula having a distal end with a larger outer diameter than the outer diameter of the remaining cannula, a first distal section adjoining the distal end, a second proximal section adjoining the first distal section, and a proximal end. A cannula housing is injection molded onto the distal end and the first distal section of the cannula and the molding core pin is removed from the cannula. A piercing needle with an outer diameter d4 is threaded into the cannula, wherein the diameter d4 of the piercing needle is chosen such that it is smaller than the diameter d1 of the molding core pin.
