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Factor VIII Activity (Serum/Plasma)

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

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.

Quick summary

["Factor VIII helps prevent excessive bleeding by aiding blood clot formation."]

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

Key facts at a glance

LOINC
63484-0
Short code
F-actin Ab SerPl Ql IF
Synonyms
F-actin Ab SerPl Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 Is This Test Done?

Your doctor may order this test if you have symptoms of bleeding disorders, such as easy bruising, prolonged bleeding from cuts, or unexplained nosebleeds. It may also be performed before surgeries or procedures that carry a risk of bleeding, or if you have a family history of clotting disorders.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is then sent to a lab for analysis to measure Factor VIII activity levels.

What Do Results Mean?

Results are typically reported as a percentage of normal activity. A result below 10% may suggest a deficiency, while higher values are within normal ranges. Exact reference ranges can vary by lab.

What Are Common Causes of Abnormal Results?

Low Factor VIII activity can be caused by inherited conditions (like Hemophilia A), liver disease, or certain medications. High levels may occur due to certain medical conditions or treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Factor VIII plays a critical role in the blood clotting process. Deficiencies can lead to excessive bleeding, which may require treatment with clotting factor replacements. Regular monitoring is important for those with inherited disorders.

Short name

Factor VIII Coagulation Activity

Frequently asked questions

What are the normal values for Factor VIII activity?
Normal values typically range from 10% to 150% of normal activity, but exact ranges can differ by lab. Your doctor will interpret results in the context of your overall health and medical history.
How long does it take to get results from this test?
Test results are usually available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will contact you once results are ready.
Can lifestyle changes affect Factor VIII levels?
While certain medications or medical conditions can influence Factor VIII levels, lifestyle factors like diet or exercise generally do not directly impact this protein’s activity. Always follow your doctor’s advice regarding any treatments or lifestyle adjustments.
  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