Venipuncture

Venipuncture is the collection of blood from a vein, usually for laboratory testing.

How is this test performed?

Blood is drawn usually from the inside of the elbow or the back of the hand. The site is cleaned with antiseptic prior to draw. A phlebotomist will wrap an elastic band known as tourniquet, around the upper arm to apply pressure to the area and make the vein swell with blood.

The phlebotomist will then gently insert a needle into the vein. The blood collects into an airtight vial or tube attached to the needle.

Once the blood has been collected, the needle is removed, and the puncture site is covered with a bandage to stop any further bleeding.

Why is this test needed?

Blood consists of two parts:

• Fluid (plasma or serum)
• Cells

Plasma contains various substances such as glucose, electrolytes, proteins, and water. Serum is the fluid part that remains after the blood is allowed to clot in a test tube. Specifically, serum is the fluid part of blood after a substance called fibrinogen has been removed by clotting.

Cells in the blood include red blood cells, white blood cells, and platelets.

Blood helps move oxygen, nutrients, waste products, and other materials through the body. It helps control body temperature, fluid balance, and the body’s acid-base balance.

Tests on blood or parts of blood may give your health care provider important clues about your health.

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Preparation

The only preparation is to limit certain medications or to avoid food and drink prior to the procedure. Your health care provider will let you know ahead of time what preparation you may have to do. After the procedure you may experience some throbbing for a short time, but that will subside.

Veins vary in size from person to person and a venipuncture is more successful on some people than others. Other risks associated with a venipuncture include infection, hematoma, fainting or feeling light headed and excessive bleeding.