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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 abnormal 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
53019-6
Short code
ENA SS-a 60kD Ab Ser-aCnc
Synonyms
ENA SS-a 60kD Ab Ser-aCnc
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 related to blood clotting disorders, such as recurrent deep vein thrombosis (DVT), pulmonary embolism, or bleeding problems. It may also be used to monitor treatment for conditions like disseminated intravascular coagulation (DIC) or hereditary clotting disorders.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn from a vein, but if it’s drawn from an arm vein, fasting isn’t required. Tell your provider about any medications or supplements you’re taking, as they could affect results.

How the Test Is Performed

A healthcare professional will collect a blood sample from a vein in your arm using a small needle. The blood will be sent to a lab for analysis to measure your antithrombin III concentration.

What the Results Mean

Results are typically reported as a percentage or mass concentration relative to a standard. Low levels may indicate an increased risk of clotting, while very low levels could suggest a hereditary deficiency or treatment-related suppression. High levels may be seen in certain medical conditions or during 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 III levels?
Low antithrombin III levels can be caused by hereditary deficiencies, certain medications (like heparin or oral anticoagulants), liver disease, or conditions that increase clotting activity, such as severe infections or trauma.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will discuss the findings with you during your follow-up visit.
Can I eat or drink before this test?
If your blood is drawn from a vein, fasting for 8–12 hours is often recommended unless instructed otherwise. If drawn from an arm vein (e.g., fingerstick), no fasting is needed, but always follow your provider’s specific 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