Von Willebrand Factor Antigen

The Von Willebrand Factor Antigen test measures the amount of von Willebrand factor (VWF) protein in your blood. VWF helps platelets stick to injured blood vessels and carries and protects clotting factor VIII, both of which are essential for normal clot formation.

This test quantifies how much VWF is present, not how well it functions. It is often ordered together with a VWF activity test and a factor VIII level to evaluate for von Willebrand disease and other causes of abnormal bleeding.

Clinicians order this test if you have frequent nosebleeds, easy bruising, prolonged bleeding after injury or dental work, heavy menstrual bleeding, or a family history of bleeding. It is also used before surgeries or procedures to help estimate bleeding risk and to plan preventive care.

Low amounts can suggest inherited or acquired von Willebrand disease. High amounts can occur with inflammation, stress, pregnancy, or aging. Your results help determine whether more testing is needed and guide treatments such as desmopressin, factor concentrates, or procedure planning to reduce bleeding risk.

A lower than expected antigen suggests a reduced supply of the protein. Your clinician may repeat the test and order companion studies, such as VWF activity, multimer analysis, and factor VIII, to clarify the type and severity of any disorder.

A normal antigen with abnormal activity can still indicate a functional problem. A higher than expected antigen may reflect your biology or a temporary response to illness or stress. Because VWF levels fluctuate, testing is often repeated when you are well and away from strenuous activity or acute events.

If your result falls outside the expected range, discuss your bleeding history and medications with your clinician. You may be advised to avoid medicines that affect platelets before procedures and to undergo targeted testing or a personalized plan for surgery or dental work.