When I was tested a year or so ago, my doc told me there are ranges of course. (say for my age the normal range was 400-700) I can tell you I was not high side, more low side, even so, no treatment from him since I was still in the range.
I also think levels can wave, so if they test me one week and it is 424, but then the next week it may be higher, so they can't pin specifics and don't just prescribe for levels in low but normal range.