Hi, late last year my sister was diagnosed with under active thyroid and she is now on 50mg levothyroxine. She's just been for another blood test and her results have come back with T4 13 and TSH 4.39. Doctor said this was fine as TSH should be between 2 and 4.5? This isn't the range I have - I've got 0.4 - 5.0 on mine? Any advice appreciated please?