Thyroid UK
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T3 only - how to check via testing?

I have been on T3 only for around 2 years and am worried about how to check if all is OK since the NHS locally do not do FT3 checks seemingly even if you are on T3 only, and my GP doesn't have a clue on how to understand the blood tests, though I have told her that if I am T3 only then my TSH will show suppressed which it does.

If I pay out Blue Horizon to do a private check what should I do or be looking for? Should I do it first thing in the morning before I take my T3, and then it would be an accurate reading of my FT3? If it is then over range this would be a bad thing?

I understand that it is not good to have an FT3 which is above the range - and could lead to bone loss and/or atrial fibrillation? Given my age (62) I am nervous of this now.

I ended up on T3 only having been on T4 only for 17 years, but was not well, was overweight, and diagnosed with ME/CFS. My GP agreed to send me to an endo of my choice as my FT3 reading (done privately) was below range.

The endo let me try T4 plus some T3 but I felt worse on this and gave up after 6 weeks which in retrospect was not long enough, and probably 20 mcg T3 was maybe not enough either.

I then asked if I could try T3 only instead and to my surprise he allowed this providing my GP agreed which she did. Since then I have lost weight, but this has stabilised for around 6 mths now and reduced my dose slightly to 50 mcg which I take in 3 doses. My BP and pulse are usually fine ie lowish/normal BP, and pulse usually in the 70s.

Last year I did try to reintroduce T4 a couple of times, but didn't feel very well on it. I did manage to reduce the T3 and managed to take 25 mcg T4, but then realised that my hair was dropping out badly and hair on my legs stopped growing entirely which concerned me. I don't really understand the connection there, but it happened each time I tried the T4.

That said, I cannot say T3 only has solved all my problems as I still have stamina issues that I know are connected with the ME/CFS and have had a mitochondrial function test done a couple of times that confirm those connections. I would be willing though to try some NDT to mix with the T3 which would reduce my intake of T3 and maybe I could tolerate the NDT better.

10 Replies

The NHS can test t3 but I don't know if it happens in all areas. My t3 was tested last time as my TSH and t4 were both significantly below range. I think the lab made the call on that one but I will check with my GP. I am also on t3 only. I had the blood drawn first thing in the morning before my morning dose of t3. Because I had education my dose following the flu (could no longer tolerate my normal dose) my t3 was at the bottom of the range. This has improved since recovering from the flu and getting back up to my usual dose.

The free t3 test can be a little random due to the short half life but it will at least give you and indication of what is going on. When you've had the tests, post them here so someone can help you interpret them. TSH and t4 should be low and t3 within range. Bear in mind that t3 may be temporarily high in the few hours immediately after taking a dose, especially if you take it all in one go. If you take smaller doses throughout the day you will not likely see such big fluctuations.

I hope that helps a little.

Carolyn x


Thanks Carolyn. I am waiting for the results of blood tests I had done at the hospital - they were doing a range of tests on other things to do with my stomach, but as I didn't know I was having the thyroid one by them I had just taken my T3 so even if they do give me an FT3 on that it will be incorrect. I am expecting them to have just done the TSH.

I could go to my GP and ask for just the thyroid tests done as they were due for an annual check anyway. However I need to specifically ask for the FT3 as previously they refused to do it unless it was privately. This seems to be ridiculous if I am on T3 only medication so I may need to speak with the GP about it first and see what she says. One one occasion I did pay the NHS for the FT3 test but that was when I was on T4 only.


If you feel o.k. I don't think it's necessary to get a FT3 test. Before the blood tests were introduced, that's how we used to get treated. Symptoms eradicated and kept on dose and if symptoms changed dose adjusted. If the doctor reduced your dose according only to your TSH that's not how to treat people, unless they were overdosed. In that case you would have obvious symptoms. You say you still have symptoms so you are not on a correct dose and this is a link which may be helpful.

I am on T3 alone and am well. I had to change my T3 as the one I was on (I didn't initially realise it) began giving me symptoms after being stable for a while on it.


Hello Shaws, thank you for your reply. I understand what you are saying re symptoms and thank you too for the link re Dr Lowe, but the problem is that not all symptoms are due to the thyroid are they? Also we don't have good physicians we can go to in the UK who can monitor us well as he clearly did.

I am not exactly 100% well as I still have symptoms of ME/CFS but it's hard to disentangle what's what as I believe some of it is separate from the thyroid issues.

That said, I do know that some of it is probably due to weak adrenals, and despite testing 3 times since 2012 I have never fully got that part sorted, and perhaps never will. I am unable to tolerate (due to sensitive stomach issues) things like Nutri Adrenal, but I do take other supplements and see a herbalist who is giving me liquorice and other herbs to help.

My last saliva test very recently showed an OKish reading when I wake, but then a sharp fall for the 2nd and 3rd reading of the day, then the last one is OK. Quite similar pattern to the previous readings, and the first one I had done in 2012 I was T4 only, so certainly no connection with being T3 only. I sent this latest test to Dr Myhill so I could get a commentary and she recommended a small dose of Pregnenolone, but I find I get anxiety after a few days with it.


Hi Agapanthus, Don't want to tread on anybody's toes here, but you do know that ME/CFS isn't a disease, Don't you? Chronic Fatigue Syndrome (sometimes call ME). A syndrome is a bunch of symptoms (therefore not a diagnosis) which are caused by something. As you are hypo, the obvious cause would be low thyroid, but could also be adrenals as you said, or nutritional deficiencies. Have you had your vit d, vit B12, folate, ferritin and iron tested? Low B12 gives symptoms very much like hypo (like CFS), B12 needs to be up the top of the range. The others should be at least mid-range. Low magnesium could also cause fatigue, and many other symptoms.

Before giving you a 'diagnosis' of CFS, your doctor should have tested things like that to find the cause of the syndrome. Sounds like you have a very lazy doctor there.

Hugs, Grey


Thanks GG. I am aware that there is controversy re the ME/CFS diagnosis by some people in the 'thyroid world' (if you will excuse the expression). I was diagnosed hypothyroid some 10 years or more before the ME diagnosis, (in my early 40s) and took the T4 meds initially which helped the condition in the first few years. In my late 40s I went downhill, and began the menopause, and put on weight, and put it all down to the menopause for a few years.

I suspect that these days I would not have been diagnosed hypo so quickly, as I was only 'borderline' but the GP then in the 1980s was prepared to start me on Thyroxine pretty quickly based on the direction of my TSH and my symptoms.

This was long before the days of the internet and even when I discovered the thyroid controversy initially I did not investigate further as I found it all rather baffling. I did read Dr Peatfield's book some 10 yrs ago but found it hard to understand the links at the time and thought I was OK as I was on thyroxine anyway, and my regular tests were 'normal' .

Since then I have done a lot of reading and exploration via forums such as this one. It was because of this that I got referred to an endo who agreed to try me on T3. I also have had tests on many many things (both thyroid/adrenal and ME related) and optimised as much as I am able to. None of the standard NHS blood tests ever showed up deficiency actually of the things you mention, but one private Dr I went to felt that the tests he did showed up some issues, so just in case I do take supplements for B12, magnesium, other B vits, D3, etc, and have done for several years now. I am sure they do make a difference, but despite all I have done my stamina remains limited. I have other symptoms such as poor immune function, and migraine aura.

I have also had a mitochondrial function test done twice now (private via Dr Myhill) which indicates that there is an issue with my mitochondrial function, plus some other things that are a bit over my head but indicate deficiency anyway. After 5 yrs of exploration and considerable cost I am at the end of my resources to do much more really, though as I said, I did redo my Adrenal Stress Test recently.

Having read and researched on both ME (scientifically based) AND Thyroid forums I have come to the conclusion that there is more to ME than the thyroid and adrenals for SOME people. It is as you say just a set of symptoms, and I believe that there are subgroups and different reasons for different people that our limited testing in the UK can not unravel. If you have money in the US (or via Dr Meirleir in Brussels) then perhaps one can find out more. Certainly in my case the logic would be that the thyroid problem is at the heart of it, but I am not totally convinced - or perhaps too much damage has been done and cannot be completely mended as I am 62 and as we

age our bodies do also.


I'm 70, so know a bit about aging. And I'm getting better and better and stronger and stronger taking the dose of T3 that I know I need - and not what some doctor/lab technician thinks I need, plus HC, plus a cocktail of minerals and vitamins. None of which would have been approved by the last doctor I saw!

With him, I got a bunch of blood tests done - as many as he would allow, although he considered vits and mins to be 'of no importance' - to give me an idea where I was, and then went it alone. I do my own research, and try things out. I Don't do blood tests for thyroid anymore, I go by symptoms. I've experimented with doses of T3 only as low as 25 and as high as 225, and have settled for 75 mcg. I take two 20 HC, one in the morning and one at lunchtime. And a long, long list of other suppléments. And I'm feeling better and better. It's low, but I know I'm on the right road.

Doctors are useless, they made me sicker and sicker until I ended up in a wheelchair. If I'd continued to listen to them, I'd be dead by now. So what have I got to lose by doing it my way? lol

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Well that is good to hear GG especially since you are older than I am - good on you! I can understand why you are doing it for yourself.

On the whole I agree with you re Drs - or at least mainstream ones. The ones I have got help from are private and non-mainstream and test for other things that could be useful.

I too have experimented but am out of ideas for now, though the herbalist is helping me as best she can with the adrenal issues and I am also trying a little Pregnenolone.


Well, only a little bit older! lol

But from all you say, my guess is you just aren't on enough T3 FOR YOU. As for the adrenals, herbs can sometimes do more harm than good. Why not try a little HydroCortisone?


Oh, there is an edit function. At the bottom you of your post, you have 'Reply' 'Recommend' and an Arrow. Click on the Arrow and it says : Edit, Delete, Report. Just click on Edit.


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