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Serum or Plasma Antithrombin III Concentration

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

This test measures the level of antithrombin III, a natural 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
54152-4
Short code
NuMA Ab Ser Ql IF
Synonyms
NuMA Ab Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 to check for conditions like clotting disorders (such as antithrombin deficiency), monitor treatment for blood thinners, or evaluate bleeding risks in certain medical situations. It may also be used in research or specialized clinical settings.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the draw if your lab uses a specific method. Avoid smoking or strenuous activity for 30 minutes before the test if instructed.

What the Test Involves

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch or discomfort, but it usually lasts only a few seconds. The blood sample is then sent to the lab for testing.

What the Results Mean

Results are typically reported as a concentration level of antithrombin III. Low levels may indicate a higher risk of clotting, while very low levels could suggest a genetic or acquired deficiency. Your provider will discuss these results with you in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Antithrombin III

Frequently asked questions

How long does it take to get results?
Results are usually available within 1 to 3 business days, depending on the lab’s processing time and your healthcare provider’s workflow. Some labs may provide preliminary results sooner, but confirmatory testing may take longer.
What causes low or high antithrombin III levels?
Low levels can result from genetic mutations, liver disease, severe infections, or certain medications. High levels may be seen in some genetic conditions or during pregnancy, though this is less common. Your provider will investigate potential causes based on your medical history and symptoms.
Can I eat or drink before this test?
Most tests do not require fasting, but if your lab uses a specific method (like some immunoassays), you may be advised to avoid food or drink for a few hours beforehand. Always follow your healthcare provider’s instructions.
  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