A lancet is a small, specialized medical instrument designed to obtain a capillary blood sample via a quick, shallow skin puncture. This device is most commonly used with a lancing device and a glucose meter to monitor blood sugar levels at home. Capillary blood sampling is far less invasive than drawing blood from a vein, making it a practical method for frequent testing. A lancet provides a small volume of blood, typically three to five microliters, which is sufficient for most point-of-care tests like blood glucose or hemoglobin checks. The controlled penetration of the spring-loaded lancing device minimizes discomfort while ensuring a viable sample is collected.
Preparing the Lancing Device and Puncture Site
Before performing the puncture, load a new, sterile lancet into the lancing device. Remove the device cap and insert the lancet until it clicks firmly into place, ensuring the needle is not touched to maintain sterility. Twist off the lancet’s protective cap, save it for safe disposal later, and replace the device cap.
Most modern lancing devices feature an adjustable depth setting that controls how far the lancet penetrates the skin. This setting should be calibrated to the user’s skin thickness. A setting of two or three is often suitable for thinner skin, while four or higher is needed for calloused or thicker skin. The maximum recommended depth is typically no more than 2.4 millimeters to avoid hitting deeper tissues. Start with a shallower setting and adjust upward if the blood sample produced is insufficient.
Selecting and preparing the puncture site is important for a successful and comfortable collection. The sides of the fingertip are the preferred location, as they contain fewer nerve endings than the sensitive pad area. Rotate the site with each test to prevent the formation of calluses and chronic soreness. Wash hands thoroughly with warm water and soap, as the warmth increases blood flow and helps a blood drop form more easily.
Step-by-Step Guide to Obtaining a Sample
Once the lancing device is loaded and the depth is set, initiate the puncture on the prepared fingertip. Press the device firmly against the chosen side of the finger to stabilize the skin surface. Holding the device firmly ensures the spring-loaded mechanism delivers a quick, controlled puncture at the set depth, minimizing tissue trauma and pain.
Activate the release mechanism while maintaining firm pressure against the skin; the lancet will quickly pierce and retract. After the puncture, gently massage the finger from the base toward the tip to encourage blood flow to the puncture site. It is important to wipe away the very first drop of blood that appears, as this initial fluid may be contaminated with tissue fluid, which could lead to an inaccurate test result.
The second drop of blood should be collected once it forms a full, rounded bead. If the blood drop is too small, continue to apply light, gentle pressure to the finger until a sufficient volume is present for the test strip to absorb. Avoid aggressively squeezing or “milking” the finger, which forces tissue fluid into the sample and compromises the accuracy of the reading.
Immediately touch the end of the test strip or collection surface to the blood drop, allowing the sample to be drawn into the strip by capillary action. The device will typically signal when enough blood has been collected and begin the analysis. Apply the blood to the strip quickly while it is still fresh from the puncture site.
Post-Test Care and Safe Disposal
Following sample collection, apply light but firm pressure to the puncture site using a clean, dry cotton ball or sterile gauze pad. Maintaining pressure for a few moments helps the bleeding stop quickly and prevents bruising. The small puncture wound usually requires only a few seconds of pressure and typically does not require a bandage.
The used lancet must be immediately and safely removed from the lancing device. Most devices have a mechanism to eject the used lancet without the user touching the exposed needle tip, which prevents accidental needlesticks. Never reuse a lancet, as this dulls the tip, increases pain, and carries a risk of infection or cross-contamination.
Used lancets are classified as sharps and must be disposed of in a designated, puncture-proof sharps container, which can be purchased from pharmacies. If an approved container is unavailable, a heavy-duty plastic container with a secure, screw-on lid, such as an empty laundry detergent bottle, can serve as a temporary alternative. This container must be clearly labeled as “USED SHARPS, DO NOT RECYCLE” and sealed with duct tape once it is three-quarters full. The used test strip can generally be placed into the regular trash, though local guidelines should always be followed for all medical waste disposal.