Hi Zahra,
I am sorry if i missed it,but did you do DNA test for your son?
Its good to maintain hb above 10 to help kids grow well,so 10 should be the pre transfusion hb if you are transfusing him regularly.That way there will be less stress on his body and bone marrow.
Children's appetite do increase after transfusion,i have noticed the same with my daughter,and they are more active as there is no lack of oxygen in the body.
I don't think there will be any fixed transfusion intervals for intermedias,if you decide to transfuse him regularly,keep his pre transfusion hb between 9 and 10,if you dont transfuse him regularly,you'll have to monitor his hb constantly,intermedias normally maintain their hb between 7 and 8, with out transfusions.
Zaini.