Antithrombin III
Antithrombin III is a protein that helps regulate blood clotting by inhibiting thrombin and other clotting factors. This test measures the activity level of antithrombin in your blood.
Category: Coagulation
Also known as: antithrombin iii, antithrombin 3, at iii, at3, antithrombin, antithrombin activity, antitrombin iii
Reference range: 80–120 % (Source: ABIM)
Standard unit: %
High values may indicate
High antithrombin III levels are uncommon and generally not clinically significant, though they may be seen with acute hepatitis or vitamin K deficiency.
Low values may indicate
Low antithrombin III levels may indicate an increased risk of blood clots (thrombosis), liver disease, disseminated intravascular coagulation (DIC), or a hereditary antithrombin deficiency.
Frequently asked questions
- What is a normal Antithrombin III level?
- A typical reference range for Antithrombin III is 80–120 % (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is Antithrombin III measured in?
- Antithrombin III is most commonly reported in %. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do Antithrombin III reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track Antithrombin III over time?
- Yes. Upload results from any lab and BloodId charts your Antithrombin III over time against its reference range, so you can see whether the trend is rising, falling, or stable.
Related biomarkers
Source: MedlinePlus, U.S. National Library of Medicine
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