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Serum or Plasma Test for Total Antithrombin III Concentration (Mass 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 problems."]

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

Key facts at a glance

LOINC
10091-7
Short code
ST I-Amp 6ms L-V4
Synonyms
ST I-Amp 6ms L-V4
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 like easy bruising, excessive bleeding, or a history of blood clots. It could also be part of a routine check for conditions like antithrombin deficiency, which can increase your risk of clotting disorders.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood sample drawn from a vein in your arm, similar to other blood tests. If you’re on blood-thinning medication, let your provider know before the test.

What the Results Mean

Results help determine if your antithrombin III levels are within normal ranges. Low levels may indicate a genetic or acquired condition that increases clotting risk, while normal levels suggest healthy blood clotting regulation.

Common Conditions Monitored

This test is often used to diagnose or monitor conditions like antithrombin deficiency, disseminated intravascular coagulation (DIC), or liver disease, which can affect protein production in the blood.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Antithrombin III

Frequently asked questions

What causes abnormal antithrombin III levels?
Abnormal levels can result from genetic mutations (inherited), liver disease (reduced production), or conditions like DIC (increased breakdown). Certain medications or pregnancy may also affect levels temporarily.
How often should I get this test?
Your provider will decide based on your medical history and symptoms. If you have a known deficiency, tests may be scheduled regularly to track changes in your levels.
Can I eat or drink before this test?
You can eat normally, but avoid heavy meals just before the blood draw. Drink water unless instructed otherwise, as it helps with vein access.
  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