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Total Antithrombin Activity (Serum)

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

This test measures how much antithrombin is present in your blood serum. Antithrombin is a natural protein that helps prevent blood clots from forming.

Quick summary

["Antithrombin helps control blood clotting and may be checked if you have a history of clots or bleeding problems."]

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

Key facts at a glance

LOINC
34675-9
Short code
mtDNA Mut Anl Bld/T
Synonyms
mtDNA Mut Anl Bld/T
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have symptoms like unexplained bruising, bleeding gums, or blood in urine/stool. It’s also checked in people with inherited clotting disorders, kidney disease, or after certain surgeries or treatments that affect blood clotting.

What to Expect Before the Test

You’ll typically have a small needle inserted into your arm to draw blood. No special preparation is needed, but inform your doctor about any medications (especially blood thinners) or recent illnesses.

What the Results Mean

Results below normal levels may indicate clotting disorders, liver disease, or conditions that damage blood vessels. Results above normal may suggest rare clotting issues or lab errors. Your doctor will interpret results in the context of your health history.

Common Conditions Linked to Results

Low antithrombin levels can be linked to conditions like disseminated intravascular coagulation (DIC), liver disease, or inherited antithrombin deficiency. High levels may rarely be seen in certain genetic conditions or after certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Antithrombin Activity

Frequently asked questions

Why might my antithrombin test be ordered even if I don’t have symptoms?
Your doctor may order this test as part of a routine checkup, to monitor a known condition (like liver disease or clotting disorders), or before certain treatments (like chemotherapy or organ transplants) that could affect blood clotting.
What if my results are outside the normal range?
If your results are low, your doctor may recommend further testing or treatments to address the underlying cause, such as medications to boost antithrombin levels or managing a clotting disorder. If high, they may investigate other factors or repeat the test.
Can I eat or drink before this test?
You can eat and drink normally unless instructed otherwise. Avoid alcohol for 24 hours before the test, as it may affect blood clotting temporarily.
  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