URL of this page: //www.nlm.nih.gov/medlineplus/ency/article/003715.htm

Alpha-1 antitrypsin test

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

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. Persons 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 doctor about the meaning of your specific test results.

What Abnormal Results Mean

A lower-than-normal level of A1AT may be associated with:


There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient 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 light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

Alternative Names

A1AT test


Niewoehner DE. Chronic obstructive pulmonary disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 88.

Update Date 8/30/2014

Related MedlinePlus Health Topics