Alpha-1 antitrypsin blood test
Quick answer: This test measures alpha-1 antitrypsin, a protein that protects the lungs and liver from damage. Doctors order it for early or unexplained emphysema, liver disease, or when the condition runs in the family.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed.
How the test is done
- 1You sit and the inside of your elbow is cleaned
- 2A needle draws blood from a vein into a tube
- 3The lab measures the AAT level
- 4If low, your doctor may order a genetic test to check the type
What your results can mean
Reading your report
Normal ranges differ between labs and by age and sex, so discuss your result with your doctor.
If the result is outside the usual range
A low level can be seen with inherited alpha-1 antitrypsin deficiency, which can lead to lung and liver disease. A high level can be seen with infection, inflammation or pregnancy, as AAT rises with them.
Who usually has this test
People with emphysema at a young age, unexplained liver disease, or a family history of AAT deficiency.
Risks and aftercare
You may have a small bruise at the needle site.
Names and options
Also called: AAT, A1AT
Listed by the hospital as
- ALPHA - 1 ANTITRYPSIN - SERUM
Questions about this test
Is alpha-1 antitrypsin deficiency inherited?
Yes. It is passed down through genes from both parents. If you are found to have it, your doctor may suggest testing close relatives.
Can an infection affect my AAT level?
Yes. AAT rises during infection or inflammation, which can hide a mild deficiency. Your doctor may repeat the test when you are well or test the gene type.
Why does smoking matter with AAT deficiency?
People with low AAT are more likely to get lung damage, and smoking speeds this up a lot. Avoiding smoke is one of the most important steps.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.