Less Common Types of Blood Tests
A small number of blood tests require just a fingerstick. A very small sample of blood from your capillaries can be obtained from the fingertip or earlobe, or from the heel of a newborn (heelstick). Warming the skin with moist compresses for about 10 minutes facilitates blood flow to the area. The skin is then pricked with a lancet. Because there are more nerves in the finger than in your elbow, you may find that a fingerstick is a bit more painful than venipuncture, although less intimidating.
In more critical situations—usually not outpatient diagnostic tests—the blood from a patient’s arteries needs to be analyzed. This procedure, known as an arterial sample, is performed by a healthcare practitioner such as a specially trained nurse. A local anesthetic may be administered and, afterward, the nurse will apply pressure to stop the bleeding and prevent a hematoma.