no it can be taken but l carn can lower the afinity of t3 but their isnt much info out there about it or how it works. so from what i understand, it doesnt surpress t3 it lessens its effects. so say you are on 100mcg t3 you will only be getting say around 25. that may be way off numbers wise but that's how i understand it. i honestly dont think it has the big of an impact at all. tons of bodybuilders are using it and still getting stupid lean. john meadows was a huge advocate for it's use when fat loss stalled out and got nasty peeled. so i really dont think it has that big of an impact. my labs have always come back good while using it with my thyroid meds so it doesnt have a huge impact on mine at all