Serum or Plasma Antithrombin III Concentration (Mass Concentration)
This test measures the amount of antithrombin III, a natural protein in your blood that helps prevent abnormal blood clots from forming. It may be checked if you have a history of clotting disorders or are taking medications that affect blood clotting.
["Antithrombin III helps control blood clotting; low levels may increase your risk of clots."]
Key facts at a glance
- LOINC
- 99105-9
- Short code
- C trach Ag SerPl Ql IA
- Synonyms
- C trach Ag SerPl Ql IA
- 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 This Test Might Be Ordered
Your healthcare provider may order this test if you have symptoms like unexplained bruising, frequent nosebleeds, or blood in urine, or if you have a family history of clotting disorders. It might also be done before surgery or if you’re taking blood-thinning medications like warfarin.
What to Expect Before the Test
No special preparation is needed, but you may fast for 8–12 hours before the test if your lab requires it. Bring any medications you’re currently taking, as they could affect results. Avoid smoking or strenuous activity for a few hours before testing.
How the Test Is Performed
A healthcare professional will draw blood from a vein in your arm using a needle. You may feel a brief pinch, but the procedure usually takes less than 5 minutes. The blood sample is sent to a lab for analysis using a specialized immunoassay method.
What the Results Mean
Results are reported as a percentage or specific concentration relative to a standard. Low levels (below normal) may indicate conditions like antithrombin deficiency, liver disease, or certain medications. High levels are less common but could suggest liver problems or pregnancy.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Antithrombin III deficiency is a genetic or acquired condition that increases your risk of blood clots. Low levels can be detected early to guide treatment, such as blood-thinning medications or lifestyle changes. Regular monitoring may be needed if you have a history of clotting issues.
Short name
Antithrombin III Level
Frequently asked questions
How long does it take to get my results?
Can I eat or drink before this test?
Will I need to do anything special after the 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