Serum or plasma concentration of antithrombin III (ATIII)
This test measures the level of antithrombin III, a natural protein in your blood that helps prevent blood clots from forming. It plays a key role in maintaining blood flow and preventing excessive clotting.
["Antithrombin III helps regulate blood clotting and supports overall vascular health."]
Key facts at a glance
- LOINC
- 56549-9
- Short code
- ENA SS-A 52kD Ab Ser IA-aCnc
- Synonyms
- ENA SS-A 52kD Ab 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
- 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 evaluate your risk of blood clots, especially if you have a history of clotting disorders, certain medications (like anticoagulants), or conditions that affect blood clotting. It may also be used to monitor treatment progress for conditions like disseminated intravascular coagulation (DIC) or inherited clotting disorders.
What Does a Low or High Level Mean?
Low levels of antithrombin III can increase your risk of blood clots, while very high levels might rarely be associated with other health concerns. Your results will be interpreted by a healthcare professional based on your medical history and symptoms.
How Is This Test Performed?
A small blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum or plasma for testing. The test measures the concentration of antithrombin III using an immunoassay method.
What Are Common Conditions Monitored With This Test?
This test is often used to diagnose or monitor conditions such as antithrombin deficiency, liver disease (which can affect protein production), or to assess the effectiveness of anticoagulant treatments.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Antithrombin III is a critical protein in the blood clotting process. Low levels can lead to an increased risk of clotting events, including deep vein thrombosis (DVT) or pulmonary embolism. High levels are less commonly associated with clinical concern but may warrant further evaluation if unexplained.
Short name
Antithrombin III Level
Frequently asked questions
What does a normal range mean for this test?
How long does it take to get results from this test?
Can I eat or drink anything before this test?
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