The time spent with Factor VIII (FVIII) levels <0.01 IU/mL is a known risk for bleeding. Conventional prophylaxis schedules follow a weight based regimen and are titrated according to clinical bleeds. FVIII pharmacokinetics (PK) may be used to optimise FVIII prophylactic regimens, maintaining adequate FVIII trough levels. This offers the possibility to not only tailor individual regimens but also may potentially reduce the rate of clinical and subclinical joint bleeding.