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Alternative namesBlood-drawing; Phlebotomy
DefinitionVenipuncture is the collection of blood specimen from a vein, usually for laboratory testing.
How the test is performedBlood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A sterile needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding .
How to prepare for the testPreparation may vary depending on the specific test, and many tests do not require any special preparation. The health care provider may limit certain medications shortly before the test or require an overnight fast to assure an accurate sample.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
Blood is used by the body for transportation of oxygen, food, waste products, and other materials within the body. It is also used for regulation of body temperature, regulation of fluids, and acid-base equilibrium. Because blood is used for multiple functions within the body, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions.
Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. Serum is what remains when fibrinogen has been removed from the plasma (this is the fluid that remains after blood is allowed to clot in a test tube). The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets .
Normal ValuesNormal results vary with the specific test.
What abnormal results meanAbnormal results vary with the specific test.
What the risks areRisks associated with venipuncture are slight:
Special considerationsVeins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Update Date: 8/18/2003Daniel Levy, M.D., Ph.D., Infectious Diseases, Greater Baltimore Medical Center, Baltimore, MD. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT