It depends on the lab the doctor used, but if he
uses QUest , request the Heptimax which is sensitive to 5 IU/mL. In he
uses LabCorp, request the Quanta Sure (that is the exact name - no more) which is sensitive to 2 IU/mL.
If he has not had a recent CBC - most doctors give orders for CBCs about every 2 weeks in the beginning of treatment to so they can watch these blood counts -- get him one, ASAP.