Skip to content

Total Antithrombin Concentration (Serum)

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

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

Quick summary

["Antithrombin III helps regulate blood clotting and may be checked if you have a history of clotting disorders or bleeding issues."]

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

Key facts at a glance

LOINC
33479-7
Short code
EBV EA-R Ab Titr Ser
Synonyms
EBV EA-R Ab Titr Ser
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 symptoms or risk factors for clotting disorders, such as deep vein thrombosis (DVT), pulmonary embolism, or liver disease. It may also be used to monitor treatment for conditions like disseminated intravascular coagulation (DIC) or hereditary antithrombin deficiency.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, similar to other routine blood tests. If you’re on blood-thinning medication, let your provider know before the test.

What the Results Mean

Low levels of antithrombin III may suggest an increased risk of clotting, while very low levels could indicate a genetic or acquired condition affecting blood clotting. High levels are less commonly significant but may be checked in certain hereditary disorders.

Common Conditions Monitored

This test is often used to diagnose or monitor conditions like hereditary antithrombin deficiency, liver disease (which can reduce antithrombin production), or to assess clotting risks in patients with trauma, surgery, or pregnancy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Antithrombin III

Frequently asked questions

What causes low antithrombin levels?
Low antithrombin levels can be caused by genetic disorders, liver disease (which impairs protein synthesis), pregnancy, or certain medications (like heparin). Chronic kidney disease or severe infections may also contribute.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you during your follow-up visit.
Can I eat or drink before this test?
You can eat and drink normally before this test, as no fasting is required. However, inform your provider if you’re taking any medications that might affect blood clotting.
  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