A lancet is a small, specialized needle used for capillary blood sampling, most commonly for blood glucose monitoring in individuals with diabetes. It is typically housed inside a spring-loaded lancing device, which controls the speed and depth of the puncture. This mechanism makes the fingerstick quick and relatively less painful than a manual prick. The device produces a small blood specimen, usually 5 to 30 microliters (µL), used to check blood glucose, hemoglobin, or other components quickly outside of a laboratory setting. The lancing device ensures the puncture is consistent, minimizing tissue damage while providing a sufficient blood drop.
Assembling the Lancing Device
The lancing device must first be loaded with a new, sterile lancet. Carefully remove the cap, often by twisting or pulling it off, to expose the lancet holder inside. A fresh lancet, encased in plastic, is then inserted firmly into the holder until it is completely seated.
Once the lancet is securely in place, the protective cap covering the needle tip must be removed, usually with a gentle twist and pull motion, taking care not to bend the exposed needle. This removed cap should be kept nearby, as it will be necessary for safe disposal later. The lancing device cap is then replaced and twisted back onto the body of the device until it is secure.
Most devices offer a mechanism to adjust the depth of the needle’s penetration, often using a numbered dial or wheel on the cap. Selecting the right depth is important because skin thickness varies between individuals and on different testing sites; a higher setting means a deeper stick. A common starting point is a medium setting, which can be adjusted lower for softer skin or higher if an adequate blood sample is not produced. Finally, the lancing device is “cocked” or primed by pulling back a plunger or sliding a barrel until a click is heard.
Performing the Blood Sample Stick
The hands should be washed thoroughly with soap and warm water, and then dried completely, as this increases blood flow to the fingers and reduces the risk of contamination. Massaging the hand and finger gently from the base toward the tip can further encourage blood circulation to the sampling site.
The optimal location for the puncture is the side of a fingertip—specifically the middle, ring, or pinky finger—rather than the sensitive pad, which has a higher concentration of nerve endings. Using the sides of the finger is less painful because there are fewer nerves and more capillaries closer to the surface. It is recommended to alternate between fingers and different sides of the same finger to prevent soreness or the development of calluses.
The primed lancing device should be pressed firmly against the chosen site on the fingertip. With a steady hand, the release button is pressed, which quickly inserts and retracts the lancet to create a small puncture. The first drop of blood that appears should typically be wiped away with a clean piece of gauze or tissue, as this initial drop may contain excess tissue fluid that could dilute the sample. A second, clean drop of blood is then collected by gently “milking” the finger, applying light pressure from the base of the finger toward the puncture site without excessive squeezing.
Proper Disposal and Safety
Once the blood sample has been successfully collected, immediate care for the puncture site involves applying gentle pressure with a clean piece of gauze or a cotton ball until the bleeding stops. This helps prevent bruising and ensures the wound closes quickly. A bandage can be applied if bleeding persists or for comfort.
The lancing device cap should be removed, and the used lancet must be shielded before being taken out of the holder. Many lancets come with a small protective cap that can be placed back over the exposed needle tip by carefully pushing the needle into the cap on a hard, flat surface. Some lancing devices have an ejector mechanism that allows the user to remove the lancet without directly touching the needle.
All used lancets, even those that have been recapped, must be disposed of in a designated sharps container. This container should be rigid, puncture-proof, and have a tight-fitting lid, such as a commercially available sharps box or a heavy-duty plastic detergent bottle. Used sharps should never be placed directly into household trash or recycling bins, as this poses a serious risk of injury to sanitation workers and others. The container should be sealed when it is about three-quarters full and then taken to a local collection site for proper medical waste disposal, following local community guidelines.