Serum Antithrombin III Concentration (Qualitative or Quantitative)
This test measures the level of antithrombin III, a natural protein in your blood that helps prevent abnormal blood clotting.
["Antithrombin III helps maintain healthy blood flow by inhibiting clotting factors."]
Key facts at a glance
- LOINC
- 107236-2
- Short code
- ENA SS-a 60kD IgG Ser IA-aCnc
- Synonyms
- ENA SS-a 60kD IgG Ser IA-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 82784
- 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 Is This Test Done?
Your healthcare provider may order this test to check if you have low levels of antithrombin III, which can increase your risk of blood clots. It may also be used to monitor treatment for conditions like disseminated intravascular coagulation (DIC) or after surgery to prevent clots.
What Does a Low Level Mean?
Low levels of antithrombin III can signal an increased risk of clotting disorders. This may happen due to inherited conditions, certain medications, or conditions that affect blood clotting, such as liver disease.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for a few hours before the blood draw if your test involves a fasting sample. Wear comfortable clothing and plan to stay near the testing site for a short time.
What Happens During the Test?
A healthcare professional will draw blood from a vein, usually in your arm. You may feel a slight pinch or sting, but it should only take a few minutes. The blood sample will be sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Antithrombin III plays a critical role in blood coagulation regulation. Deficiencies can lead to hypercoagulability, increasing the risk of venous thromboembolism (blood clots) or other clotting disorders. Monitoring levels helps guide treatment decisions for patients with inherited or acquired antithrombin deficiency.
Short name
Antithrombin III (ATIII) Test
Frequently asked questions
What causes low antithrombin III levels?
How is antithrombin III tested?
Can antithrombin III levels change over time?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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