Take an antihistamine an hour before your Levothyroxine. If the rash and itching eases then it is likely you are allergic to one of the ingredients in that brand and you should try an alternative. There are 4 brands available in the UK:
Mercury Pharma 25mcg, 50mcg, 100mcg.
Actavis (also known as Almus or NorthStarr) 50 & 100mcg
Try the antihistamine first in case it's nothing to do with Teva.
If your TSH is >2 you are undermedicated and that is why your FT3 is low. It's nothing to do with poor conversion. You can't establish poor conversion before you are optimally dosed. If TSH is 0.3 - 1.00 and FT4 high in range and FT3 is low then you are a poor converter.
Get tested for copper before taking anything that contains it. Hypos usually have high copper and low zinc, so you don't want to add more copper on top.
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