Blood lancets are used to prick the skin in skin testing for allergies and are generally disposable. Lancets are always used with A blood-sampling device, which is a reusable instrument (lancet pen/lancing device) equipped with a lancet. It is always applied in blood glucose and other diagnostic tests. It is also most commonly used by diabetics during blood glucose monitoring. The variety of point configurations and penetration depths to suit most capillary blood requirements.