A tight strap (a tourniquet) is wrapped around your upper arm. The skin around the chosen vein is cleaned and then a small needle is inserted into the vein and a small blood bottle is then attached to collect the sample. After the needle is removed a piece of gauze is placed over the puncture site and you will be asked to press on the area for a few minutes. Bleeding usually stops very quickly but may take a little longer if you are on blood thinning medications.