Optimal free T3 range

Why is it that hypothyroid persons are encouraged to have free T3 levels in the upper range of normal?

[Marz]

T3 is the Active hormone and needed in every cell of the body - so good levels needed so there is enough to go around the whole body.  Over range is not good as one could go Hyper so having it as high as possible is surely good ?

[DellFinium]

Re: 'more reliable' - I have read otherwise on this forum (no, can't remember when/where/who!) so have never bothered with the 24 hour urine - but has anyone compared T4/T3 ratios in blood vs urine?  Do they correlate or does the urine test show a more marked difference?  Anyone?  

[faith63]

The best way to dose t3, is by elimination of symptoms,  not labs.  I will never believe that thyroid labs, which show what is in the blood, will show how are cells are responding to the thyroid meds..no matter what any one else says.