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Factor VIII Activity (Plasma) – Clia

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

This test measures how well your blood clots due to a protein called Factor VIII. It’s often checked if you have bleeding problems or are at risk for clotting disorders.

Quick summary

["Factor VIII helps control bleeding; low levels may indicate hemophilia or other clotting issues."]

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

Key facts at a glance

LOINC
34590-0
Short code
vWF Cp Inhib PPP Ql
Synonyms
vWF Cp 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
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 symptoms like excessive bleeding (e.g., nosebleeds, heavy periods, bruising easily), a family history of bleeding disorders, or if you’re planning surgery. It can also help diagnose conditions like von Willebrand disease or hemophilia.

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 thinners, let your doctor know before the test.

What the Results Mean

Results are compared to a standard range for healthy adults. Very low levels may mean bleeding problems, while very high levels could indicate clotting risks or certain medical conditions.

Common Conditions Linked to Results

Low Factor VIII activity is often linked to hemophilia (a genetic disorder causing bleeding), von Willebrand disease (a bleeding disorder), or acquired clotting deficiencies. High levels may be seen in certain liver diseases or after blood transfusions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test helps diagnose bleeding disorders, assess risk for clotting events, and guide treatment decisions—such as medication or blood transfusions—if needed.

Short name

Factor VIII Coagulation Factor

Frequently asked questions

What causes Factor VIII levels to be low?
Low Factor VIII levels can result from genetic mutations (e.g., hemophilia), certain medications (like blood thinners), liver disease, or autoimmune conditions that damage blood proteins.
How often should I get this test?
Frequency depends on your symptoms, medical history, and treatment plan. Your doctor will determine how often to check, especially if you have a bleeding disorder or are on Factor VIII replacement therapy.
Can diet or lifestyle affect Factor VIII levels?
Dietary factors like vitamin K (found in leafy greens) can influence clotting proteins, but Factor VIII itself isn’t directly affected by diet. Lifestyle habits (e.g., smoking) may indirectly impact liver function, which can affect blood clotting.
  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