Thyroid UK
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Converting to T3

Sorry to ask even more questions about converting T4 to T3?. I think I may not be converting properly as I feel more unwell after being diagnosed, and taking 125mg Levothyroxine. Since taking Levo I now realise how well I was before diagnosis!. My question! We are told to take our medication without fail, otherwise we could become very ill, even be life threatening! BUT! If we are not converting our daily Levothyroxine T4 to T3 is the medication having zero effect on our thyroid problem, because,if it is not achieving what it is supposed to? Is it a waste of time, could I take a Cadburys chocolate button instead? far more enjoyable in my opinion, and probably as useless for my thyroid problem as Levothyroxine!!?

4 Replies

One of the problems with talking about conversion is that it is not a simple case of "you convert" or "you do not convert".

Conversion occurs in the thyroid, liver, kidneys, skeletal muscle, heart, hair follicles, brain, and elsewhere. Some of the converted T4 is used where it is converted. But some is released into the bloodstream and used elsewhere.

Some conversion may be occurring - but not enough, or not in the right places, or, umm, ????

Your simple question, which makes perfect sense as a question, simply does not seem capable of being fully and usefully answered with current state of knowledge, so far as I am aware.



I imagine your GP has not tested your FT3 level?


Hi Red Apple, No, bit scared to ask! not very approachable at my medical centre!


It is quite common to not convert properly.What is your Ft3 ( with ranges). I need mine near the top of range, without T3 I am under range If your T4 is high and you still do not feel could be the answer. T3 on a script helps lots of symptoms especially weight. It also lowers the TSH , which means a lot of GP`s are wary of it. Most endos like it!

Best wishes,



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