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Alpha-1 Antitrypsin Activity, Serum/Plasma

Published: August 9, 2026Updated: August 16, 2026

A blood test that measures the functional activity of alpha-1 antitrypsin, a protein that helps protect the lungs and liver.

Quick summary

["This test helps evaluate alpha-1 antitrypsin levels and function when deficiency or related lung or liver disease is suspected."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
34697-3
Short code
A1AT Act/Nor SerPl
Synonyms
A1AT Act/Nor SerPl
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

Alpha-1 antitrypsin activity is a laboratory measurement of how well this protective protein works in the blood. The test may be used along with alpha-1 antitrypsin concentration and genetic testing to evaluate possible deficiency.

Why might I need this test?

Your clinician may order this test if you have unexplained chronic lung disease, a family history of alpha-1 antitrypsin deficiency, or liver disease that could be associated with low alpha-1 antitrypsin levels.

How is the test performed?

A blood sample is collected from a vein and tested in the laboratory to determine the activity of alpha-1 antitrypsin. It is usually reported as a concentration of enzyme activity, with the laboratory providing its own reference interval.

How do I prepare for the test?

Fasting is generally not required, but follow any instructions from your clinician or laboratory. Certain medicines and treatments for alpha-1 antitrypsin deficiency can affect the result, so tell the laboratory about them and do not stop prescribed treatment without medical advice.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Alpha-1 antitrypsin activity

Frequently asked questions

Does this test diagnose alpha-1 antitrypsin deficiency?
It can help identify or evaluate possible deficiency, but genetic testing and an alpha-1 antitrypsin concentration are often needed to confirm the diagnosis and identify the specific gene variant.
Is fasting required for this test?
Fasting is usually not required. Follow the instructions provided by your clinician or laboratory if they give specific preparation directions.
What can affect alpha-1 antitrypsin activity?
Inflammation, liver disease, smoking, and certain medicines or treatments can influence the result. Your healthcare professional will interpret it alongside your symptoms, examination, and other laboratory findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy