The fingerstick device should be held firmly against the puncture site. To obtain the best capillary specimen using the finger, align the puncture device perpendicular (horizontal) to the whorls of the fingerprint. This cross-cut of the fingerprint whorls causes the blood to bead at the puncture site, allowing the phlebotomist to efficiently collect the drops of blood into the container. This image illustrates the correct position of the cut in relation to the fingerprint lines.
If the puncture is made parallel to the fingerprint whorls (as shown below), the blood will not bead, but rather it will travel down the channels between the lines of the fingerprint. This makes it difficult to collect the blood into the container. The phlebotomist may inadvertently "scrape" the blood from the skin while filling the container, resulting in hemolysis and/or clotting of the specimen.
The tip of the finger should be avoided. Puncturing the fingertip may cause unnecessary discomfort to the patient.