A blood sample is needed.

There is no special preparation.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

This test is helpful in identifying a rare form of emphysema in adults and a rare form of liver disease (cirrhosis) in children and adults caused by an AAT deficiency. AAT deficiency is passed down through families. The condition causes the liver to make too little of AAT, a protein that protects the lungs and liver from damage.

Everyone has two copies of the gene that makes AAT. People with two variant copies of the gene have lower blood levels and are at risk for more severe disease. Different gene variants may cause differing severity of illness.

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

A lower-than-normal level of AAT may be associated with:

• Damage of the large airways in the lungs (bronchiectasis)
• Scarring of the liver (cirrhosis)
• Chronic obstructive pulmonary disease (COPD)
• Liver tumors
• Yellowing of the skin and eyes due to blocked bile flow (obstructive jaundice)
• High blood pressure in the large vein that leads to the liver (portal hypertension)

There is little risk involved with 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:

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

A1AT test

Dietzen DJ, Willrich MAV. Amino acids, peptides, and proteins. In: Rifai N, Chiu RWK, Young I, Burnham C-AD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. St Louis, MO: Elsevier; 2023:chap 31.

Han MK, Lazarus SC. COPD: diagnosis and management. In: Broaddus VC, Ernst JD, King TE, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 7th ed. Philadelphia, PA: Elsevier; 2022:chap 64.

Masson VK, Boas SR. a1 - Antitrypsin deficiency and emphysema. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 442.

Updated by: Allen J. Blaivas, DO, Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.