Bloods
Clotting: APPT (prolonged as intrinsic pathway affected,
may be normal if mild case; corrects with mixing study);
PT (NAD as extrinsic pathway not affected)
FVIII and IX assays (low/absent), other factors (vWF, FV, VII, XI, XII etc.)
FBC (platelets NAD), LFTs (liver makes clotting factors)
Genetic testing (X-linked)
Inhibitor screening if indicated
Genetic testing for family