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Serum or Plasma Mass Concentration of Antithrombin III

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

This test measures the amount of antithrombin III, a natural protein in your blood that helps prevent abnormal blood clotting. Low levels may indicate a higher risk of clotting disorders.

Quick summary

["Antithrombin III helps regulate blood clotting; low levels may signal inherited or acquired clotting risks."]

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

Key facts at a glance

LOINC
86122-9
Short code
S pneum Da 11A IgG Ser-mCnc
Synonyms
S pneum Da 11A IgG Ser-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 Is This Test Done?

Your healthcare provider may order this test if you have a history of blood clots, certain blood disorders, or conditions that affect protein production in the liver. It may also be checked before surgeries or treatments that increase clotting risk.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it is analyzed to measure the protein concentration of antithrombin III.

What Are Common Reasons for Abnormal Results?

Low levels of antithrombin III can occur due to liver disease, pregnancy, certain medications, or inherited conditions. High levels may be less common but could be seen in some genetic or metabolic disorders.

How Is the Test Performed?

The test uses a blood sample collected in a tube, which is then processed to determine the mass concentration of antithrombin III through a specialized laboratory method.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Antithrombin III Level

Frequently asked questions

What does a low antithrombin III level mean?
A low level may suggest an inherited clotting disorder or conditions that reduce protein production, such as liver disease. Your doctor will discuss next steps based on your overall health and symptoms.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on lab processing times and your healthcare provider’s workflow.
Can I eat or drink before this test?
You can usually eat and drink normally before this test unless instructed otherwise by your doctor. Blood tests do not require fasting unless specified for other reasons.
  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