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Factor VIII Activity (Plasma) – Prophylactic or Monitoring Measurement

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

This test measures the activity level of Factor VIII, a protein essential for blood clotting. It helps monitor treatment effectiveness or assess bleeding risks in people with hemophilia or von Willebrand disease.

Quick summary

["Factor VIII levels guide treatment decisions and bleeding prevention strategies."]

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

Key facts at a glance

LOINC
99614-0
Short code
Emicizumab PPP-mCnc
Synonyms
Emicizumab PPP-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
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 Matters for Your Health

Factor VIII is a critical clotting factor. Low levels can lead to excessive bleeding, especially after injuries or surgeries. This test helps doctors track how well your body is producing this protein or how well your treatment is working.

How the Test Works

Blood is drawn from a vein, and the plasma is analyzed using a specialized immunoassay method to measure Factor VIII activity. This helps determine your risk for bleeding and whether your treatment is effective.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid certain medications that could affect results. Tell your doctor about any recent injuries, surgeries, or symptoms of bleeding.

What the Results Mean

Results are expressed as a percentage of normal activity. Very low levels may indicate hemophilia or von Willebrand disease, while higher levels may suggest treatment response or other conditions. Your doctor will interpret results in the context of your medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Role in Diagnosis and Treatment

Short name

Factor VIII Level

Frequently asked questions

Why might my doctor order this test?
Your doctor may order this test if you have a history of bleeding disorders, are receiving Factor VIII replacement therapy, or are preparing for surgery. It helps ensure safe blood clotting and guides treatment adjustments.
What happens if my Factor VIII level is low?
If your levels are low, you may be prescribed Factor VIII replacement therapy to prevent or manage bleeding episodes. Your doctor will monitor your levels regularly to adjust treatment as needed.
Can diet or lifestyle affect this test?
Diet or lifestyle factors generally do not affect Factor VIII levels directly. However, certain medications (like blood thinners) or infections can influence clotting. Always inform your doctor about all medications or supplements you take.
  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