An apparatus for eliciting a blood sample comprises a housing, an aperture in a wall of the housing, an aperture cover moveable between a first position in which the aperture is covered and a second position in which the aperture is uncovered, the aperture cover comprising a sealing member configured to seal the aperture on a first side of the wall when the aperture cover is in the first position and a user-contactable part extending from the sealing member through the aperture to the second side of the wall and configured to allow a user to move the aperture cover between the first and second positions.