Thyroid UK
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Is T3 what I need?

I have been on T4 for underactive thyroid for 20 years, taking 150/125 mcg alternate days. My recent annual test of T4 and TSH showed a very low TSH (0.03) and high T4 (24) - I don't have the ref. ranges. T3 was not tested, and I have had to ask for this to be done next time. I have always felt that the synthetic thyroxin did not make me feel as healthy as before my diagnosis, but recently I have realised that some of the symptoms I currently have (feeling the cold, overheating, tired, find it hard to motivate myself... I could go on) are very likely to be due to my thyroid condition.

The GP I saw has agreed to repeat the tests in 3 months' time (- in the meantime I am on 125mcg levothyroxine), along with requesting that the lab does a T3 test as well as kidney, liver and full blood count tests.

I am wondering if I am not converting T4 to T3. Do my tests suggest that? If the next round of tests don't help, I will probably try T3 myself. Any thoughts please?

6 Replies

Do you take any supplements? Have you been tested for low iron/ferritin, B12, Vit D etc? All these things can give similar symptoms. Not saying you don't need T3 but always good to have tried everything to rule out any problems that are not necessarily T4 related.

There is an article that I am sure that someone will be able to quote from that states that T3 may be an option to be added. I take T3 only so definitely not against T3.


I have been taking a full range of good quality vitamins and minerals for many years - although there is no iron in any of the capsules I take. So low iron is possible, but if I now start supplements of iron I'm not sure how that may affect the next round of blood tests, in June.


definitely best to get it tested before treating it. How about Vit D?


I don't think Vit D can be a problem, my regular vitamin capsules contain 125% of the RDA and I do take them every day. I don't think the GP tests will include iron (ferritin) altho' presumably a full blood count will indicate?


I took cod liver oil and a mult vitamin ((vit D2) and have a healthy diet and go outside frequently (allotment holders) and I was still deficient in vit D3. My husband was the same. It surprised us too. A FBC will give some clues but it won't give what your iron stores are.


I had read that Iron needn't be a worry and that B vits are more energising. Also I checked my vit D spray is 1500% RDA which I find is great and my friend takes between 3-5 sprays of this a day to help her.

I take 100mcg T4 and about 18mcg T3 daily but still getting some symptoms though no where near as many as I used to. T3 was the turning point in my recovery - good luck!


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