To understand hemophilia, it’s helpful to know how the body normally works when it comes to stopping a bleed. When a person bleeds, 13 different proteins—called clotting factors—work together to form a blood clot.
In people living with hemophilia, one of the clotting factors is missing or reduced, which prevents this process from working. They have trouble forming blood clots—so it’s harder to stop bleeds when they happen.