Factor XII Activity (Hemophilia Factor XIIa Activity)
This test measures the activity level of Factor XII, a protein involved in the blood clotting process. It helps assess inherited or acquired bleeding disorders related to this clotting factor.
["This test evaluates your blood’s ability to clot properly through Factor XII function."]
Key facts at a glance
- LOINC
- 47285-2
- Short code
- Heparin CF II Ag PPP-aCnc
- Synonyms
- Heparin CF II Ag PPP-aCnc
- 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
- 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
Doctors may order Factor XII activity testing if you have symptoms of bleeding disorders, such as excessive bruising, prolonged bleeding from cuts, or unexplained nosebleeds. It’s also used in research or specialized cases where Factor XII-related clotting issues are suspected, such as in hemophilia or rare clotting factor deficiencies.
What to Expect Before the Test
No special preparation is needed. You’ll have a small needle inserted into a vein (usually in your arm) to draw blood. The process is quick and typically painless. If you’re on blood thinners, your doctor will advise you to stop them temporarily before testing.
What the Results Mean
Results are compared to a standard range to determine if your Factor XII activity is within normal limits or if it’s too high or too low. Abnormal results may indicate inherited bleeding disorders or other clotting-related conditions.
Common Conditions Linked to Factor XII Testing
Factor XII activity testing is primarily used to diagnose or monitor conditions like hemophilia (specifically Type XII deficiency) or other rare clotting disorders. It’s less common for routine screening but may be part of a broader evaluation for unexplained bleeding or clotting issues.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Factor XII plays a role in the intrinsic pathway of blood clotting, which helps initiate the cascade that leads to clot formation. Low levels of Factor XII can lead to prolonged bleeding times, while high levels may rarely be associated with clotting risks. This test helps identify genetic or acquired deficiencies that could affect bleeding control.
Short name
Factor XII Activity
Frequently asked questions
What does a low Factor XII activity level mean?
How long does it take to get Factor XII test results?
Can Factor XII testing be done at home?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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