Contrastingly, persons with severe hemophilia on prophylaxis experience fluctuating FVIII levels, often returning to FVIII levels under or around 1 IU/dL, not seen in persons with nonsevere hemophilia A. These repetitive low FVIII trough levels, seen before administration of prophylaxis, are expected to increase the overall bleeding hazard. This evidence concerns the gene F8 and hemophilia.