High Reverse T3 - what does it mean?: I had a... - Thyroid UK

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High Reverse T3 - what does it mean?


I had a blood test done about a month ago and am trying to work out what results mean. I know the high Anti-Tg abs means Hashimotos but what does the high Reverse T3 mean and how does that interact with my conversion of T4?

I'm on 100mcg of Levothyroxine but still have a quite a lot of symptoms and problems with weight, headaches, PMS, aches & pains etc. etc.

these are my Thyroid results (I can post vitamins too if it's relevant)

TSH: 2.61 0.27 - 4.20 IU/L

T4 Total: 101.0 64.5 - 142.0 nmol/L

Free T4: 16.28 12 - 22 pmol/L

Free T3: 3.78 3.1 - 6.8 pmol/L

Reverse T3* H 32.0 10 - 24 ng/dL

Reverse T3 ratio L 7.69 >20 Ratio

33 Replies

This is an explanation of RT3 which will be helpful as many have misconceptions as to what RT3 means. The two questions/answers will be helpful:


By the way - your TSH is too high, Dr Toft (ex President of the British Thyroid Association) recommends:-

6 What is the correct dose of thyroxine and is there any rationale for adding in tri-iodothyronine?

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).

Even while taking the slightly higher dose of levothyroxine a handful of patients continue to complain that a sense of wellbeing has not been restored. A trial of levothyroxine and tri-iodothyronine is not unreasonable. The dose of levothyroxine should be reduced by 50µg daily and tri iodothyronine in a dose of 10µg (half a tablet) daily added"

The above is from a Pulse online article and email louise.warvill@thyroiduk.org.uk if you require a copy but some doctors still ignore this advice.

claudiasmum in reply to shaws

So in summary, is Dr Lowe saying that Reverse T3 is only ever temporary so not actually an issue which should be taken into account in determining thyroid function?

shawsAdministrator in reply to claudiasmum

He knew more than most and I'd go along with his views. I'd say yes to your query. Dr Lowe himself took 150mcg of T3 in the middle of the night as he had Thyroid Hormone Resistance.

claudiasmum in reply to shaws

Interesting and very different to much of what you see on this forum including the responses below....

shawsAdministrator in reply to claudiasmum

This is more info on Dr L. He was an Adviser to Thyroiduk.org.uk.

He was also Director of Fibromyalgia Research Foundation and Thyroid Science - published lots of info:



Underpinning Dr. Lowe's work are his two main intellectual interests: (1) theoretical-deductive science, which enables one to make the best possible sense of study findings in a research field; and (2) symbolic (mathematical) logic, the discipline one uses to determine the validity or invalidity of his own and others' conclusions and arguments.

Dr. Lowe is a devout critical rationalist. This means that he subscribes to the hypothesis (proposed by Sir Karl Popper and articulated by David Miller and others) that the ultimate job of logical, scientific thinkers is to formulate bold hypotheses, and rigorously try to falsify them. The reason for falsifying the hypotheses is to eliminate errors in them and perhaps the entire hypotheses. Free of at least some of their errors, ideas, beliefs, hypotheses, and theories may become more accurate representations of truth, which is correspondence with truth. If eliminating errors makes it obvious that an idea, belief, hypothesis, or theory is entirely false, then we can—having learned from the falsification—replace it with one that is hopefully more accurate.

sulamaye in reply to claudiasmum

Not everyone agrees with dr Lowe. It depends if the stress in your life /on your body is persistent. Dieting causes rt3 it is a stress on the body, an underlying illness like lymes where a bacteria has gone underground and is attacking your body can cause rt3. Being overdosed on thyroxine meds can cause high rt3 as a way of balancing. Ongoing emotional stress etc.

claudiasmum in reply to sulamaye

But I am guessing that if RT3 is a way of slowing you down to protect your body in times of stress then you need to be tackling the underlying causes rather than taking more T3 to defeat your body's natural mechanisms. Although understandably taking more T3 will make you feel better in the first instance it might hide the true problems. I think I might be in that situation now....

sulamaye in reply to claudiasmum

I think in theory that is a good approach. But it assumes that you can identify the stressors. So in my case I can't identify what the stress is because nobody knows what is the cause of ME is, but I know that taking T3 only gives me A better quality of life then if I take anything with T4 in it. And there is the argument that the extra energy produced by having my cells working better can be used for healing whereas three years of doing nothing didn't make me better. So yes I think it's very complicated and if you can identified stressor and remove it or reduce it that's the first line of attack. But as you know it can all be a bit of a vicious circle with cortisol affected and affecting thyroid which becomes a bit chicken and egg.

claudiasmum in reply to sulamaye

Yes you are right. I know what my current stressor is (trigeminal neuralgia) and trying to do something about it but my thyroid function has plummeted as a result. I am taking more NDT than usual. I guess I will be benefiting from the extra T3 in it but wonder if the T4 is turning into RT3 at the same time. All very interesting anyway.

Just an anecdote that may be of interest... One of the forum members (who no longer posts on Thyroid UK) improved her trigeminal neuralgia by treating herself with high dose vitamin B12. She was able to come off some (or possibly all) of her pain meds.

You can see her posts here, so it may be worth poking around to see if you can find posts where she discusses it :


Thank you for that humanbean. Will take a look as this is just the most awful thing to have. I am already taking Vit B12 supplements orally but who knows if it is reaching where it needs to go. I was severely deficient a few years ago.

What dosage of B12 are you taking, and what kind?

I am not sure what the units are - am at work so can't check the bottle - but they are 500s. I was on 300 per day to start with then told to cut down to 100 for maintenance but my symptoms returned so I went up to 500 without doctor's authority. I buy them from Holland & Barrett. I know immediately when I am going low because I get migraines - they are my first symptom.

The best form of B12 for most people is methylcobalamin (there are always exceptions though).

Most H&B B12 products are cyanocobalamin, and the body has to convert it into methylcobalamin. If you aren't that good at converting you might not be getting much benefit from your B12.

I take 5000 mcg methylcobalamin per day. 500 mcg doesn't sound much for someone who has previously been deficient.

If you want to try the higher dose methyl-B12, many of us buy the Jarrow Formulas or Solgar methylcobalamin tablets.

They work best if they are stuck under the tongue and allowed to dissolve slowly - no sucking or chewing.

You can't overdose on B12 by the way.

VTUI in reply to claudiasmum

To claudia's mum: My understanding is that B12 is best taken sub lingually, or by injection. VTUI

Yes post your vitamin results too as if you are insufficient in any it makes a huge difference.

Are you gluten free? Absolute must with Hashimotos to feel well.

I was just on Levo but have now switched to NDT (bought from Thailand) and gone gluten free and added the vitamins I'm deficient in and I'm definitely so much better than I was. Sticking to gluten free with no cheats makes a big difference. You may also need to watch your dairy. It's easier than you think once you get your head round it!

Dr Datis Khazzarian has a website and some great books out. Also the Immune System Recovery Plan by Susan Blum M.D is very interesting and helpful to us Hashis. It has a workbook to help with our food intolerance. Highly recommend.

I see Shaws is advising on other questions re RT3.

Good luck.

Hidden in reply to Katepots

I do believe you probably mean gluten free - Glutton is a different term altogether :-) It may seem silly to point it out, but for those who are new to their research, if they go looking for foods which are 'glutton free' they will struggle to find any.

claudiasmum in reply to Hidden

It did make me chuckle though - wish I could find some glutton free food!

Katepots in reply to Hidden

Hahaha stupid phone! Yes I did!

claudiasmum in reply to Katepots

That's actually a very funny auto correct!

Raucous in reply to Katepots

Hi Katepots - Thought I'd just post the whole thing I got done. I'm now taking B12 (methylcobalamine), Vit D & K2, Selenium & Zinc & GP prescribed iron after I showed her the results (2 x 200mcg a day). It is hard to work out when to take them all though!

Maybe I should have had more vitamins tested but this was the package from Blue horizon.

Yes I am investigating Gluten free and will probably go for that but still trying to decide whether to try adding T3 or try NDT instead. I think I may try T3 first.


CRP 1.50 <5.0 mg/L

Ferritin L 7.7 20 - 150 ug/L

Thyroid Function

TSH 2.61 0.27 - 4.20 IU/L

T4 Total 101.0 64.5 - 142.0 nmol/L

Free T4 16.28 12 - 22 pmol/L

Free T3 3.78 3.1 - 6.8 pmol/L

Reverse T3* H 32.0 10 - 24 ng/dL

Reverse T3 ratio L 7.69 >20 Ratio


Anti-Thyroidperoxidase abs 11.0 <34 kIU/L

Anti-Thyroglobulin Abs H 192.2 <115 kU/L


Vitamin D (25 OH) 64 (Deficient <25 nmol/L

Insufficient 25 - 50

Consider reducing dose >175 )

Vitamin B12 364 (Deficient <140 pmol/L

Insufficient 140 - 250

Consider reducing dose >725)

Serum Folate 30.90 10.4 - 42.4 nmol/L

Katepots in reply to Raucous

I'm not the best one to decipher blood results although it doesn't look like you have Hashimotos as your TPO result is low.

Your Thyroglobulin antibody (TGAb) is high — this antibody targets thyroglobulin, the storage form of thyroid hormones.

I would think adding T3 or changing to NDT will make the difference.

I'm pretty much on same vitamins.

You should also feel a difference in how you feel as Vit D and B12 deficiencies make you feel dreadful. You should have less pain, feel less tired and less muddled!

I'd ask Clutter of one of the other Admin staff to read results for you.

The most obvious issue with these results is that you are underdosed. Most people feel well with a TSH close to, or under 1. But more important are the freeT4 and especially freeT3. FreeT4 should be in the top quarter, and freeT3 should be in the top third. Both of yours are close to the bottom.

I don't know enough about rT3 to comment. I only know vague things about it being made out of the T4 (levothyroxine) you're taking, and often meaning you're taking too much. Obviously you're not taking too much. But your freeT3 is fairly low relative to your freeT4. T3 is the active hormone that your cells and organs actually need. T4 is just the storage hormone, it needs to be converted by your cells into T3. Sometimes it gets converted into rT3 instead, which is supposed to regulate how much you've got, it is a useless form, that competes with T3 and blocks it getting into your cells.

One solution to this is to take T3 instead of T4. You may struggle to find a doctor who will support this. Self medicating is an option, many people on this forum do it.

I know and I asked my doctor if I could go up from 100 to 125 levo but she said no! She said she could only go by the NHS guidelines & is both sympathetic and patronising. She did ask if I was depressed and I'm sure would have been quite willing to prescribe anti-depressants but I said no. Like you say self-medicating seems the only answer - just pricey and time consuming!

A member here always makes the very funny comment - what blood test told her you were deficient in anti-depressants ;)

Rt3 is basically a dud T3.

It's something to do with the conversion of T4, when the iodine molecule is on the inside its T3 and when it's on the outside its RT3. It's the wrong size and can't be absorbed into the cells. They also start to build up and block the way for the healthy T3's to get into the cells.

That's a very basic explanation, but it helped me understand them!

So ideally, to fit in with the STTM guide, your FT4 should be mid range, your FT3 should be top range, and your RT3 should be bottom range - under 11.

However there's the all important rt3 ratio, which should be greater than 20. Yours is very low.

So yes, it looks like you're undermedicated, but I'd order some T3 because as you put more T4 into your body, it's just going to make more and more RT3's. You'll feel worse for it.

Obviously taking T3, and reducing your Levo, your body doesn't have to convert - it's already done. There's a chapter on reducing rt3 in STTM. Do check it out.

As previously said, your doctor may not be able to prescribe T3, so if you obtain it he/she hopefully will support you. It doesn't cost much to buy online, but the pharma charges it out at about £300 to the NHS. It's criminal.

I'm not medically trained, I'm not admin, and this is just regurgitating what I've read. Mostly from STTM and Dr Lowe's writings. I hope it helps.

T3MARY in reply to MichelleBerko

Brilliant thank god someone can explain it in layman terms thank you

MichelleBerko in reply to T3MARY

Welcome T3Mary x

Lovely description thanks - what is STTM?....lots of reading to do i think!

You're welcome!


They are the leading advocates for NDT treatment. They have closed Facebook groups called FTPO, just search them. There's a book too, but all the info is on their FP pages with commentary.

Ah yes I've got the book but haven't read it all yet. I will search for FB groups.

Good explanation!

A high RT3 and low end FT3 basically means there's not enough FT3 gettin into the cells, the other cause/s can be which is common with hypothyroidism, even though in range, is low zinc, B12, plus an MCV (MEAN CORPUSCULAR VOLUME) is over 85 even in the range, means you likely have low stomach acid, stomach acid is a requirement for these nutrients to be absorbed and a healthy gut, your first line of defence. Plus your likely low in healthy bacteria in this case... Zinc iron and copper are nessicary for adrenal health also, maybe part of the problem too... Investigation needed I feel.

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