Blood is usually drawn from an artery in the wrist. It may also be drawn from an artery on the inside of the elbow, groin, or other site. If blood is drawn from the wrist, the health care provider will first check the pulse. This is to make sure blood is flowing into the hand from the main arteries in the forearm (radial and ulnar arteries).

The procedure is done as follows:

• The area is cleaned with antiseptic.
• A needle is inserted. A small amount of anesthetic may be injected or applied before the needle is inserted.
• Blood flows into a special collecting syringe.
• The needle is removed after enough blood is collected.
• Pressure is applied to the puncture site for 5 to 10 minutes to stop the bleeding. The site will be checked during this time to make sure the bleeding stops.

If it is easier to get blood from one location or side of your body, let the person who is drawing your blood know it before starting the test.

Preparation varies with the specific test performed.

Puncture of an artery may be more uncomfortable than puncture of a vein. This is because arteries are deeper than veins. Arteries also have thicker walls and have more nerves.

When the needle is inserted, there may be some discomfort or pain. Afterward, there may be some throbbing.

Blood transports oxygen, nutrients, waste products, and other materials within the body. Blood also helps control body temperature, fluids, and the balance of chemicals.

Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains substances dissolved in the fluid. The cellular portion is made up mainly of red blood cells, but it also includes white blood cells and platelets.

Because blood has many functions, tests on the blood or its components may give valuable clues to help providers diagnose many medical conditions.

Blood in the arteries (arterial blood) differs from blood in the veins (venous blood) mainly in its content of dissolved gases (oxygen and carbon dioxide). Testing arterial blood shows the makeup of the blood before any of its contents are used by the body tissues.

Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.

An arterial stick is done to get blood samples from arteries. Blood samples are mainly taken to measure gases dissolved in the arterial blood. Abnormal results may point to breathing problems or problems with the body's metabolism. Sometimes arterial sticks are done to get blood culture (testing for infection) or blood chemistry samples.

There is little risk in having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Multiple punctures to locate veins
• Infection (a slight risk any time the skin is broken)

There is a slight risk for damage to nearby tissues when the blood is drawn. Blood can be taken from lower-risk sites, and techniques can be used to limit tissue damage.

Blood sample - arterial

Eiting E, Kim HT. Arterial puncture and cannulation. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 20.

Smith SF, Duell DJ, Martin BC, Gonzalez L, Aebersold M. Specimen collection. In: Smith SF, Duell DJ, Martin BC, Gonzalez L, Aebersold M, eds. Clinical Nursing Skills: Basic to Advanced Skills. 9th ed. New York, NY: Pearson; 2016:chap 20.

Updated by: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.