Skip to content

Factor XII Activity (Plasma)

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

This test measures the activity level of Factor XII, a protein involved in the body’s natural blood-clotting and inflammatory processes.

Quick summary

["Factor XII activity helps assess bleeding or clotting disorders and inflammation-related conditions."]

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

Key facts at a glance

LOINC
96454-4
Short code
Fact II Inhib PPP Ql
Synonyms
Fact II Inhib PPP Ql
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
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

What Is Factor XII?

Factor XII, also called the contact factor, plays a role in activating other proteins in the clotting cascade and the complement system, which helps fight infections. While its exact function is still being studied, it may also contribute to inflammation and vascular health.

Why Might This Test Be Ordered?

Your doctor may order this test if you have symptoms of bleeding disorders (e.g., excessive bruising, prolonged bleeding), signs of clotting issues, or suspected inflammatory conditions. It can also be part of a broader evaluation for hereditary or acquired coagulation disorders.

How Is the Test Performed?

A blood sample is drawn from a vein, typically in your arm. The plasma portion is separated and tested for Factor XII activity using a specialized clotting assay. Results are reported as a percentage or ratio compared to a standard reference.

What Do Results Mean?

Results may be described as decreased (lower than normal), normal, or increased (higher than normal). Abnormal levels can indicate inherited or acquired disorders affecting clotting or inflammation, though interpretation depends on clinical context.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Factor XII Activity

Frequently asked questions

Is Factor XII testing common for routine health checks?
No, this test is generally not routine. It’s typically ordered for patients with suspected bleeding disorders, clotting abnormalities, or inflammatory conditions. Your doctor will determine if it’s appropriate for your situation.
What symptoms might lead to this test?
Symptoms that could prompt this test include unexplained bruising, nosebleeds, heavy menstrual bleeding, or signs of clotting problems (e.g., blood clots in unusual places). If you have a family history of coagulation disorders, this test may also be considered.
How long does it take to get results?
Results are usually available within 1–3 business days, depending on lab processing times and your healthcare provider’s workflow.
  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