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Serum/Plasma Substance Concentration (Electrochemiluminescence Immunoassay) for Antithrombin III

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

This test measures the amount of antithrombin III, a natural protein in your blood that helps prevent blood clots from forming.

Quick summary

["Antithrombin III helps regulate blood clotting; low levels may increase clot risk or bleeding risk depending on your condition."]

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

Key facts at a glance

LOINC
31628-1
Short code
ENA SM+RNP Ab Ser Ql
Synonyms
ENA SM+RNP Ab Ser Ql
Category
chemistry
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

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have a history of blood clots, bleeding disorders, or are taking medications that affect blood clotting. It may also be checked before surgery or during treatment for conditions like liver disease or inherited clotting disorders.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

Results help determine if your antithrombin III levels are within normal range or if they need adjustment for your treatment plan. Very low levels may require monitoring or treatment to manage clotting risks.

Common Causes of Abnormal Results

Low levels can occur due to liver disease, pregnancy, or certain medications. High levels may be less common but could relate to conditions like liver disease or certain genetic factors.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Antithrombin III (ATIII) Level

Frequently asked questions

How does antithrombin III relate to my health?
Antithrombin III is crucial for preventing blood clots. Low levels can increase your risk of clots, especially if you have a history of them or take blood-thinning medications. High levels may rarely be associated with bleeding risks or other conditions, so results are used to guide treatment decisions.
What should I do if my results are outside the normal range?
If your results are low, your healthcare provider may recommend lifestyle changes, medications, or further testing to manage your condition. If high, they may investigate underlying causes or adjust treatments. Always follow their guidance.
Can I eat or drink before this test?
You can eat and drink normally unless instructed otherwise. Avoid alcohol before the test, as it may affect blood clotting proteins.
  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