System for withdrawing body fluid from a body part in particular the finger pad, comprising a compression unit that is deformed when the body part is pressed against it and increases the internal pressure in a region of the body part, and a withdrawal device. Deformation of the compression unit partially converts the primary pressing movement into a secondary movement which leads to an increase in the internal pressure in a region of the body part. The invention also comprises a system for stimulating the outflow of body fluid using a deformable compression unit.