A blood sampling device comprises a housing (20) having an aperture (29) in a forward end thereof. A lancet body (30) with an associated sharp tip (36) is located within said housing. A cap (32) is provided which has a stem portion (33) which at least partially covers the tip (36) and extends forwardly through aperture (29) opening to merge with an externally accessible tab portion (31). A locking arrangement (39, 29) is provided for restraining forward movement of said cap (32) and being twistably releaseable from a locked position to a released position. The locking arrangement comprises respective abutments (39) on said stem portion (33) and said housing, which are aligned to block forward movement of the cap (32) when it is in the locked position. When the cap is twisted to its free position the abutments allow forward movement from a pre-firing to an armed position. At least one of the abutments (39) is resiliently movable to allow it to be snapped rearwardly past the cooperating abutment during assembly.
