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Factor Xa Activity (Antithrombin Complexed)

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

This test measures the activity of Factor Xa, an enzyme involved in blood clotting, often assessed in the context of anticoagulant monitoring or inherited bleeding disorders.

Quick summary

["This test helps evaluate blood clotting function and may guide treatment for conditions like clotting disorders or anticoagulant therapy."]

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

Key facts at a glance

LOINC
96453-6
Short code
Fact XI Act + Inhib Pnl PPP
Synonyms
Fact XI Act + Inhib Pnl PPP
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
coag
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 Is Done

Your doctor may order this test if you have a suspected bleeding disorder (such as Factor X deficiency), if you’re taking anticoagulants like warfarin or low-molecular-weight heparin, or if you’re experiencing unexplained bleeding or clotting issues. It can also be part of routine screening for inherited clotting disorders.

How the Test Works

Blood is drawn and mixed with a substance that activates Factor Xa. The test measures how quickly the enzyme converts another clotting factor into its active form. This helps determine whether Factor Xa is functioning normally or if it’s impaired.

Sample Collection and Preparation

A small sample of blood is collected from a vein, typically in the arm. The blood is processed to separate plasma (the liquid part containing clotting factors) and then analyzed in a lab using specialized equipment to measure Factor Xa activity.

What to Expect Before the Test

No special preparation is usually needed, but if you’re on anticoagulants, your doctor may advise adjusting your medication timing. Avoid eating or drinking anything (except water) for a few hours before the test if specified.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low Factor Xa activity may indicate inherited clotting disorders, liver disease (which affects clotting factors), or severe bleeding. High activity could suggest rare inherited conditions or overactivation of clotting pathways. Monitoring this test helps manage anticoagulant therapy to prevent excessive bleeding or clots.

Short name

Factor Xa Activity

Frequently asked questions

What Does a Low or High Result Mean?
A result below normal may mean you have a bleeding risk, especially if combined with other clotting factor deficiencies. A result above normal is less common but could indicate unusual clotting activity or lab error. Your doctor will interpret results in the context of your symptoms and medical history.
How Often Should This Test Be Done?
If you’re on anticoagulants, your doctor may schedule this test regularly (e.g., weekly or monthly) to monitor your dose. For inherited disorders, tests may be done less frequently unless symptoms change. Follow your healthcare provider’s instructions for timing and frequency.
Can Diet or Medications Affect This Test?
Certain medications (like anticoagulants, antiplatelets, or steroids) can alter clotting factors, including Factor Xa. Avoiding grapefruit juice or certain supplements (e.g., ginkgo, ginseng) may help stabilize results. Always inform your doctor about all medications or supplements you’re taking.
  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