A lancet is a small, disposable medical instrument designed to obtain a tiny blood sample, typically from the fingertip, through capillary blood sampling. It facilitates the collection of the small volume of blood necessary for various screening and diagnostic tests, most commonly for monitoring blood glucose levels. The lancet is not the entire device used during a fingerstick, but the sharp component within the housing that performs the puncture. Its design focuses on creating a quick, shallow incision to access the capillaries near the skin’s surface.
The Basic Needle Design
The core of a lancet is a very fine, short needle or blade, usually constructed from sterile steel. This sharp component is housed within a small plastic cylinder, capped to maintain sterility until use. Needle thickness is measured using the gauge system, where a higher gauge number signifies a thinner needle. Common sizes for fingersticks range from 28-gauge to 33-gauge, with finer needles (like 33-gauge) influencing the sensation felt during the procedure. The needle tip is engineered for quick, controlled penetration, sometimes featuring a specialized bevel to minimize tissue trauma.
The lancet’s disposable nature is maintained by a small plastic cap that must be twisted off before loading it into a delivery device. This cap ensures the needle remains sterile and protected from contamination before the skin puncture. Once the cap is removed, the needle is intended for single use only; the tip dulls quickly, and reusing it increases discomfort and the risk of infection. Some designs, particularly safety lancets, incorporate a small, sterile blade instead of a point, which may yield a larger blood volume than a fine needle.
Variations in Lancing Devices
While the lancet is the needle component, it is almost always used with a lancing device that controls the puncture action. One common type is the adjustable lancing pen, which resembles a thick, retractable pen. A disposable lancet is loaded into this pen-style body, and a spring-loaded mechanism rapidly launches the needle into the skin when a button is pressed. This device allows the user to set the depth of penetration using a numbered dial, making it suitable for different skin types and testing locations.
A second main category is the safety lancet, a fully self-contained, single-use unit that does not require a separate pen device. These are typically small plastic modules activated by pressing the device against the skin or pushing a button. The needle is fully enclosed before use and automatically retracts into the housing immediately after the puncture. This retraction feature prevents accidental needlesticks after use, which is often required in clinical settings and makes disposal safer.
Precision and Function
The design of the lancet and its device aims to obtain a sufficient blood sample with minimal discomfort. The spring-loaded delivery system ensures the puncture is performed quickly and consistently, which helps reduce perceived pain. The ability to adjust the depth of penetration, especially in lancing pens, controls the volume of blood collected. A shallower puncture, perhaps 0.9 millimeters, may be adequate for modern glucose meters that require very small blood samples.
Conversely, a deeper setting, up to 2.4 millimeters in adults, or the use of a thicker needle or blade, produces a larger drop of blood needed for certain diagnostic tests. Increasing the depth of penetration is the primary factor that increases both the resulting blood volume and the intensity of the pain experienced. The development of finer needles and precise depth controls allows the user to balance the need for adequate blood volume with minimizing the discomfort of the skin prick.