Factor VIII activity test
Quick answer: This test measures the activity of factor VIII, a clotting protein that is low in haemophilia A. It is ordered for unexplained bleeding or a long APTT, to diagnose haemophilia A or von Willebrand disease, and to check carriers.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed; tell staff about any blood thinners or factor treatment you have had.
- In fertility careWomen who carry haemophilia may be tested before or during pregnancy to plan a safe delivery.
How the test is done
- 1Blood is drawn into a light-blue citrate tube
- 2The tube is filled to the line and sent to the lab promptly
- 3Your plasma is mixed with plasma that lacks factor VIII
- 4The clotting time is compared with a standard to give the activity
What your results can mean
Reading your report
Stress, pregnancy and hormones can raise levels; discuss your result with your doctor.
If the result is outside the usual range
A low level can point to haemophilia A, carrier status in women, or von Willebrand disease. A high level can be seen with stress, pregnancy and inflammation, and is linked to a higher clot risk.
Who usually has this test
People with a long APTT or unusual bleeding, people with a family history of haemophilia, and women who may be carriers.
Risks and aftercare
Bruising is possible; press firmly for longer if you bleed easily.
Names and options
Also called: factor 8 assay, FVIII, haemophilia A test
Listed by the hospital as
- FACTOR VIII ACTIVITY, PLASMA
Questions about this test
Can women have low factor VIII?
Yes, women who carry haemophilia A can have low levels and bleeding symptoms such as heavy periods. Testing helps plan pregnancy and delivery.
Should a haemophilia carrier be tested before pregnancy?
Carriers are often advised to have their levels checked and see a specialist before pregnancy. Testing options for the baby can also be discussed.
Why is factor VIII tested with von Willebrand factor?
Von Willebrand factor protects factor VIII in the blood. So a low von Willebrand factor can also lower factor VIII.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
Get directions ↗IVF Pulse fertility care at Tamara Hospital →
Reception
Waiting area
IVF lab
This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.