A common procedure in which a vein, usually in the forearm, is pierced with a needle to inject fluid or withdraw blood. A tourniquet is used to swell the veins, and a sterile needle is inserted. A syringe is attached to the needle if blood is to be taken or medication injected. For intravenous infusion, a cannula (tube) is inserted via the needle. After the fluid has been injected or withdrawn, the needle or cannula is removed. The area is then covered and pressure applied to stop any bleeding. The procedure is not usually painful but may cause some discomfort.


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