Factor VIII Activity (Plasma)
This test measures the activity level of Factor VIII, a protein essential for blood clotting. Low levels can increase bleeding risk.
["Factor VIII helps control bleeding by aiding clotting; results guide treatment if bleeding disorders are suspected."]
Key facts at a glance
- LOINC
- 58493-8
- Short code
- Fact VIII Ab PPP Ql IA
- Synonyms
- Fact VIII Ab PPP Ql IA
- 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 doctor may order this test if you have symptoms of bleeding disorders, such as excessive bruising, prolonged bleeding from cuts, or unexplained nosebleeds. It’s also used to monitor treatment in people with known Factor VIII deficiency (hemophilia A).
What to Expect Before the Test
You’ll typically have a small needle inserted into your arm or hand to draw blood. If you’re taking blood thinners, your doctor may adjust your medication before testing. Avoid activities that cause bleeding for 24 hours before the test.
What the Test Results Mean
Results are usually reported as a percentage of normal activity. A result below 1% strongly suggests a bleeding disorder, while levels between 1% and 50% may indicate mild to moderate risk. Your doctor will interpret results in the context of your symptoms and medical history.
Potential Side Effects
The most common side effect is mild pain or bruising at the injection site. Rarely, blood tests can cause allergic reactions or infections at the needle site. If you experience severe pain, swelling, or signs of infection (like fever), contact your doctor.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Coagulation Factor VIII Level
Frequently asked questions
Factor VIII deficiency is the most common inherited bleeding disorder. Low levels can lead to spontaneous bleeding, especially in joints or muscles. Early diagnosis and treatment (such as Factor VIII replacement therapy) can prevent complications like joint damage or chronic bleeding.
If you’re pregnant or planning to become pregnant, discuss any bleeding concerns with your doctor, as Factor VIII deficiency can affect pregnancy outcomes if untreated.
No special preparation is usually needed, but avoid eating or drinking for 2 hours before the test if instructed. If you’re diabetic, check with your doctor about timing your insulin or blood sugar medication.
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