My sister is 26 and has followed me down the hypothyroid path; I have no idea whether she's been tested for antibodies but I'd bet the farm on her being positive for them. I was 19 when I was diagnosed and that was 20 years ago.
She's currently on 25mcg levo per day and when I asked her for her last test results she said that one of them was 5 and the other 13. I'm guessing that the former is TSH and the latter fT4 (usual average UK ranges: don't have the specific ones to hand). Her GP did not increase her dosage as all was in range. She tells me that she feels okay but frankly I do find this a bit difficult to believe: when my fT4 is around 13 I find it difficult to move, let alone think, in a straight line. I really want to help her but how can I get her to understand how important it is not to just accept being 'in range'? I don't want to come over as bossy and that I know what's best for her, except that on this I really think I do (thanks, HU).
I also know that I've been *exceptionally* lucky over the years to have had a succession of GPs who did not merely leave me 'in range' but actively sought to dose me adequately so I've not had to fight this particular battle myself.
All thoughts on how to proceed gratefully received.