Alpha-1 Antitrypsin


Alpha-1 antitrypsin is a laboratory test to measure the amount of alpha-1 antitrypsin (A1AT) in your blood.

Alternative Names

A1AT test

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

There is no special preparation.

How the Test will Feel

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.

Why the Test is Performed

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 A1AT deficiency. A1AT deficiency is passed down through families. The condition causes the liver to make too little of a protein that protects the lungs and liver from damage.

Everyone has two copies of the gene that makes A1AT. Most people with a lower-than-normal level of A1AT have one normal gene for A1AT, and one abnormal gene. People with two abnormal copies of the gene have more severe disease.

Normal Results

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

What Abnormal Results Mean

A lower-than-normal level of A1AT 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 leads to the liver (portal hypertension)


There is very 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:

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


Chernecky CC, Berger BJ. Alpha1 -antitrypsin - serum. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:121-122.

Winnie GB, Boas SR. a1-antitrypsin deficiency and emphysema. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 393.

Review Date: 8/23/2016

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