Blood is usually taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow. A fine needle is gently inserted into a vein, and the tourniquet is removed.
Blood flows through the needle and is collected in a syringe or vial.
After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding. The blood is then sent to the lab for testing. An individual is often asked not to eat anything for at least 8 or 12 hours prior to the test. By visiting this site, you agree to the terms and conditions of our Visitor Agreement .