I’ve seen doses vary quite a bit according to the person and their weight.  I’m currently on 4mg (2mg am + 2mg pm) but have been on as much as 12.5mg/day (and i was really not happy and very very chunky).  This is something you should definitely discuss with your doctor.  In addition to measuring 17OHP, testosterone, androstenedione and renin, you also have to gauge how you feel.  Prednisone is typically given twice a day.