Skip to content

Factor VIII Activity (Plasma) – Antihemophilic Factor Activity

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.

Quick summary

["Factor VIII helps your blood clot properly; low levels can increase bleeding risk."]

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

Key facts at a glance

LOINC
90225-4
Short code
Fact VII Act + Inhib Pnl PPP
Synonyms
Fact VII Act + Inhib Pnl PPP
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
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

What Does This Test Measure?

Factor VIII is a clotting factor produced by your liver. It works with Factor IX to help blood clot when you have an injury. Without enough Factor VIII, your blood may not clot properly, increasing the risk of bleeding.

Why Might You Need This Test?

Doctors may order this test if you have symptoms like excessive bleeding (e.g., bruising easily, nosebleeds, or heavy menstrual periods) or if you have a known bleeding disorder like hemophilia. It’s also used to monitor treatment for clotting disorders.

Sample Collection and Preparation

A blood sample is taken from a vein, usually in your arm, and sent to a lab for testing. Plasma (the liquid part of blood after clotting) is used for this test.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any medications (especially blood thinners) or recent injuries that could affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Factor VIII Activity

Frequently asked questions

Low Factor VIII activity may suggest hemophilia or other inherited bleeding disorders. High levels can sometimes be seen in certain liver diseases or after blood transfusions. Results help guide treatment decisions, such as medication or lifestyle adjustments.
This test is typically performed using a clotting assay to measure how quickly blood clots under controlled conditions. Results are often reported as a percentage of normal activity.
What does a low Factor VIII activity mean?
A low result may indicate a bleeding disorder like hemophilia A, which requires medical management (e.g., clotting factor replacement). Your doctor will discuss next steps based on your symptoms and lab findings.
Can diet affect Factor VIII levels?
Diet generally does not directly impact Factor VIII levels, but certain medications (like blood thinners) or liver conditions can. Always follow your doctor’s advice regarding supplements or medications.
  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