A return spring arrangement for a lancet (6) is provided by a pair of undulating plastic webs (14) formed integrally with the lancet. The undulations of the two webs (14) are shown out of phase with one another. These webs (14) are flexible and thus are caused to concertina when the tips (15) of the webs hit the interior of a lancet holder on release of a drive spring. The energy stored within the collapsed webs (14) is then released to drive the lancet back within the lancet holder. This positive return of the lancet ensures that a needle (5) will retract safely into the lancet holder, after operation, and does not rely on the spring being locked into the lancet holder and onto the lancet.