Clotting Factor Level Affects Severity

Hemophilia can be mild, moderate, or severe depending on how much of the clotting factor is in a person’s blood. The normal range of factor VIII and factor IX is between 50% and 150%.

  • If you have mild hemophilia (6% to 49% factor activity), bleeding is often infrequent and typically occurs only after injury, trauma, or surgery, including dental procedures. About 25% of people with hemophilia have a mild form of the condition.
  • If you have moderate hemophilia (1% to 5% factor activity), bleeding tends to occur after minor injuries; incidents of spontaneous bleeding without an obvious cause may occur, but it is rare. About 15% of people with hemophilia have a moderate form of the condition.
  • If you have severe hemophilia (<1% factor activity), you may experience bleeding after injury, trauma, or surgery; however, you may also experience spontaneous bleeding into joints and muscles. Repeated bleeding into joints can cause a joint condition known as hemophilic arthropathy, that can result in physical disability. About 60% of people with hemophilia have a severe form of the condition.