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RT3 within range, but right at the top of range; would appreciate opinions whether I should pursue possibly adding T3 to my daily regimen


I have hypothyroidism with high TPO Abs. I'm on 50mcg levothyroxine a day.

I've just paid to have my thyroid hormones tested as I've never been tested for FT3 or rT3 before and these are my results:


FREE THYROXINE 17.95 pmol/L (12.000 - 22.000)

FREE T3 4.76 pmol/L (3.100 - 6.800)

REVERSE T3 24 ng/dL (10.000 - 24.000)

As you can see my reverse T3 is right at the high end of the normal range. I would greatly appreciate opinion as to whether I should pursue possibly adding T3 to my regimen.

Many thanks in advance for any opinions on this.


4 Replies

Spicer21 Hopefully someone will come along who has knowledge of rT3, mine is very scanty so I can't offer any suggestions there.

From your test results, it looks as though you're not actually converting T4 to T3 particularly well. For good conversion the ration of FT4:FT3 needs to be 4:1 or lower. Yours is 4.19 : 1 so you might benefit from a little help.

However, your dose of 50mcg is very low, it is really a starting dose. Just raising your Levo to get your FT4 a bit higher may help with conversion so that would be a good place to start.

Also, as you have high TPO antibodies, you have autoimmune thyroiditis aka Hashimoto's disease. Antibodies will fluctuate and attack your thyroid until it is eventually destroyed. You can help yourself by trying to reduce the antibody attacks. Adopting a 100% gluten free diet will help reduce the attacks. Gluten contains gliadin (a protein) which is thought to trigger autoimmune attacks so eliminating gluten can help reduce these attacks. Supplementing with Selenium is also supposed to help reduce the attacks.

What are your recent NHS thyroid tests like? What does your GP say? Will you show him and discuss these Blue Horizon tests? He probably wont know anything about rT3, possibly wont know much about Hashi's either. And if he's guided by TSH alone he wont consider increasing your levo.

The aim of a treated hypo patient is for the TSH to be 1 or below, or wherever is needed for the FT4 and FT3 to be in the upper part of their ranges. This quote from a Pulse Online magazine article written by Dr Toft (past president of British Thyroid Association and leading endocrinologist) explains:

"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.

In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.

But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.

This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."

If you email louise.warvill@thyroiduk.org.uk she will let you have a copy of the article which you can print out and show your GP.

1 like

Hi SeasideSusie

Thanks so much for replying. (Love your name by the way :) Wish I were at the seaside today!)

I wondered if that might be the case, i.e. that I'm not converting T4 to T3 particularly well. I've been in a bit of a quandary about seeing whether someone would be willing to prescribe me T3 though, in case taking more T3 might increase my rT3. (I'm still trying to understand how these things work.)

Thankfully, I've been eating gluten free since circa the time I was diagnosed with hypothyroidism. (I wish I'd started earlier as I wonder whether eating gluten could have triggered my hypothyroidism.) Anyway, I was having gut problems and thought it might help and it did to a certain degree. It's certainly a bonus to know that being gluten free might be helping to reduce antibody attacks on my thyroid. I will supplement with selenium now too - Am glad you mentioned that :)

My last NHS thyroid hormone tests (May 2016) were FT4 15.7 (12 - 22) and TSH 0.93 (0.3 - 5.0). (My docs never/won't test for T3 at all.)

The thyroid hormone tests that I recently had done privately (July 2016) were done via Medichecks. I was considering bypassing my GP and going straight to a private endocrinologist but, armed with Dr Toft's article, I'll give it a go and see what they say about increasing my T4. The trouble is that, as far as they're concerned, I'm technically 'euthyroid' as my test results are within range and thus they consider it's a 'job done'. I end up having to see a different GP every time I go to my local practice and I think that all of them have gone solely by the TSH results, but maybe they will be convinced to up my T4 a little when they see the information in Dr Toft's article. I'll email Louise, just as you suggest, for a copy of his article. Wish me luck! :)

Thanks once again,



Spicer21 I have found a little bit of information about rT3, not sure if it applies to you because your FT4 isn't as high as I would have thought it should be for rT3 to be a problem, but worth knowing maybe.

Apparently reverse T3 is made from too much T4 and the way to deal with it is to stop the T4 medication so no more rT3 is made, and treat with T3 only until the rT3 is cleared. It is a temporary thing so once rT3 is within the normal range you stop the T3 only treatment and presumably go back onto your normal thyroid meds. [Therefore, adding T3 to your Levo wont increase your rT3 because rT3 is made from too much T4 (levo)]

Too much to get my head around at the moment I'm afraid but have a look at these couple of articles:



But I'm not sure that applies in your case because your FT4 isn't high. On your latest results FT4 at 17.95 is 55% through range (May it was 37%). FT4 should be in the upper third of the range, ie around 19+.

Your recent FT3 at 4.76 is approx 45% through range. FT3 should be in the upper quarter of the range, ie 5.9+

So you can see you are falling short of where your FT4 and FT3 should normally be for someone to feel well.

But of course, all of this will be alien to your GP so you'd probably be flogging a dead horse there.

My instinct is telling me that you should first try a bit more Levo to get your FT4 up which will hopefully convert well and improve your FT3. I would push your doctor for this, showing him Dr Toft's article, reminding him that 50mcg Levo is a starting dose, telling him of any residual symptoms you still have, and that you would like to try an increase. I used to get around this with my old (nice, understanding, listening but sadly now retired) GP by saying "Of course, if I experience any symptoms of over medication, and I know what they are, then I will immediately reduce my dose and come back to see you". [If necessary, mention that you have looked at NHS Choices who recommend Thyroid UK as their source of information and it appears that FT3 is the most important result and that dosing should not be by TSH].

If you do consider going privately to an endo, be aware that those who also work within the NHS will probably still follow NHS guidelines and you may be no better off. To find a more understanding endo then email louise.warvill@thyroiduk.org.uk and ask her for the list of the more thyroid friendly endos.

Do update when the time comes :)

PS - you might not want to be at my seaside today, we had some rain this morning and since then it's been overcast, quite breezy and much cooler. However, this suits me better than yesterday's blistering heat, and my dog is much happier today too!

1 like

Hi SeasideSusie,

I hope the weather is better for you at the coast today.

Thank you so much for the links re rT3 etc., and all of your really valuable tips and advice. I shall definitely see if I can get my T4 increased at least a bit as I think you're right about me possibly needing more T4. If I get no joy, I'll go to an endo privately and will bear in mind what you advise about making sure that they are more open minded than the NHS endos usually are.

I'm still working my way through the links - really informative - thank you! :) And yes, I'll be glad to keep you informed re my progress.

Do I take it that you're on T4 alone at present?

Just thought I'd mention to you that I'm also having this thyroid genetic testing done (DIO2 (Deiodinase 2 Gene) Genetic Test) as per thyroiduk.org.uk/tuk/testin... which might be interesting. I should get the results in approx., 3-4 weeks.


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