The normal range of FIX and FVIII in people without haemophilia is 50% to 150% of normal, however, FIX values >125% and FVIII values >100% may be associated with increased thrombogenicity.40, 41, 42 There does not appear to be an issue in FIX gene transfer, which is associated with FIX activity at the lower range of normal. Here, F8 is linked to hemophilia.