Factor VIII Activity (Plasma)
This test measures the activity level of Factor VIII, a protein essential for blood clotting. Low levels may indicate bleeding disorders or inherited clotting deficiencies.
["Factor VIII helps your blood clot properly; low levels can increase bleeding risk."]
Key facts at a glance
- LOINC
- 3215-1
- Short code
- Fact VIII Ag PPP IA-mCnc
- Synonyms
- Fact VIII Ag PPP IA-mCnc
- 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
- ia
- 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 healthcare provider may order this test if you have symptoms like excessive bleeding (e.g., bruising, nosebleeds, or heavy menstrual periods), a history of bleeding disorders, or if you’re planning surgery. It’s also used to monitor treatment for hemophilia or von Willebrand disease.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. If you’re on blood-thinning medication, let your provider know before testing.
Test Results and Interpretation
Results are expressed as a percentage of normal activity. A result below 1% is severely low, while 1–50% may indicate mild to moderate deficiency. Your provider will discuss findings with you.
Common Conditions Linked to Low Factor VIII
Low Factor VIII activity is most commonly associated with hemophilia (especially hemophilia A) or von Willebrand disease. Other rare conditions, like acquired clotting factor deficiencies, may also cause similar symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Severe Factor VIII deficiency increases the risk of spontaneous bleeding, especially in joints or muscles. Early diagnosis allows for timely treatment with clotting factor replacement therapy to prevent complications. Regular monitoring helps track treatment effectiveness and adjust doses as needed.
Short name
Coagulation Factor VIII Level
Frequently asked questions
What causes Factor VIII deficiency?
How is Factor VIII deficiency treated?
Can lifestyle changes help manage Factor VIII deficiency?
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