Factor VIII is a critical clotting protein involved in the intrinsic pathway of blood coagulation. It works alongside Factor IX to activate Factor X, which is essential for blood clot formation. A deficiency in Factor VIII causes Hemophilia A, a genetic disorder that leads to difficulty forming blood clots, resulting in prolonged bleeding episodes, especially after injury or surgery.

The Factor VIII test measures the activity or level of this clotting factor in the blood. Low levels of Factor VIII confirm the diagnosis of Hemophilia A, which is typically inherited in an X-linked recessive manner and primarily affects males. The test is used to diagnose Hemophilia A, assess its severity, and guide treatment decisions, such as Factor VIII replacement therapy to prevent or control bleeding episodes.