A guidance mechanism for a lancing device. The guidance mechanism includes a piston having a shaft, a plurality of wings or fins extending from the shaft, a plurality of sliding engagement structures, and a lancet holder； and a chassis having a body, a plurality of longitudinal slits or cutouts, a plurality of elongated engagement structures, and an end aperture. The piston slides within the chassis, and the wings/fins engage within the slits/cutouts, allowing for linear longitudinal guidance of the piston within the chassis.
