Rt3 - ft4 0 and rt3 still high!? : After... - Thyroid UK

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Rt3 - ft4 0 and rt3 still high!?

Dawid86 profile image

After 9 months on t3 only, due to high rt3,finally my ft4 is ZERO, at this point i should have low or zero rt3.

How is possible to have high rt3 while ft4 is zero !?

Usually people clear rt3 in 3-4months using t3 only to suppress tsh 24/h.

I feel better about mind, mood, some energy, now I have high in range Testosterone, finally good cortisol!


29 Replies
SeasideSusie profile image

How is possible to have high rt3 while ft4 is zero !?

High rT3 can be caused by many things, not necessarily related to the thyroid, eg Chronic fatigue, Acute illness and injury, Chronic disease, Increased cortisol (stress), Low cortisol (adrenal fatigue), Low iron, Lyme disease, Chronic inflammation. Also selenium deficiency, excess physical, mental and environmental stresses. Also Beta-blocker long-term use such as propranolol, metoprolol, etc. Physical injury is a common cause of increased RT3, also illnesses like the flu. Starvation/severe calorie restriction is known to raise RT3. Diabetes when poorly treated is known to increase RT3. Lyme disease. Cirrhosis of the liver. Fatty liver disease. Any other liver stress Renal Failure. A fever of unknown cause. Detoxing of high heavy metals.

My rT3 increased when I added T3 despite my FT4 reducing.

I think you were told the answer about RT3 5 months or so ago...not only does T4 ‘break down’ into RT3 but so does T3...any excess that the body cannot use is cleared out of your system. So high intake of T3 ( and some still produced by your thyroid) might be still creating RT3. Plus lots of other conditions affect RT3 production from low calorie diets, acute illness/injury, chronic disease, raised cortisol, low iron etc etc. Perhaps your body does need some T4; I’d tried the T3 only dosing (as have fibromyalgia as well as hypothyroid and Hashimoto’s ) without any improvement to pain and exhaustion, yet also no obvious symptoms of over medication, and am now trying to add some T4 back again! Some of the forum administrators prefer the 75% thru range of FT4 and FT3 to feel good, I never did this as was concentrating on trying to raise FT3 to over halfway as was poor converter of T4. It’s a very long and slow process, with too many steps back instead of forward for me alas.

Oops sorry repeating causes of RT3 Seasidesusie’s post not there when I replied.

not only does T4 ‘break down’ into RT3 but so does T3...any excess that the body cannot use is cleared out of your system

Um… no. I really don't think that T3 can 'break down' into rT3 - not that 'break down' is the right term. T4 converts to rT3 by removing the wrong iodine atom for T3 - if you see what I mean. But, T3 having been produced, it cannot then change the position of that iodine atom to become rT3. It has to stay as T3 until it's converted into T2.

Yes I knew about the ‘shift’ from T4 to RT3, but without being scientific think of it differently thus the ‘ ‘ ( those ‘5’ pronounced ‘prime’ is over my head at the moment, or say in the last 5 plus years) .. , and am I right in thinking I have read that RT3 can become T3? I had too much of a deteriorating brain recently on high T3 dose only that i’ve gone back to adding some T4...one or maybe more of the supposedly inactive ‘Ts’ seems to be needed by me! At least my sentences are coherent, if inaccurate...seems like some progress.

No, RT3 cannot 'become T3' either. It is deiodinated to T2, then T1 and then eliminated from the body.

Thank you, I thought it was odd when I read it...like me there is some odd understanding of it all on some posts/ replies.. ...unfortunately trying to learn at a time when my brain is only functioning at 50% ( or less)!

helvella profile image
helvellaAdministrator in reply to MaisieGray

Even that is questionable!

It appears that some (possibly quite a bit) of T3 goes down the sulfation pathways:

Evaluation of the urinary T3 metabolite pattern demonstrated that the major products of T3 metabolism were T3 sulfate and 3,3-diiodothyronine sulfate. These observations confirm previous results suggesting that the majority of nondeiodinative T3 disposal occurs via T3 sulfate formation.


Haven't time at the moment to do further digging.

helvella profile image
helvellaAdministrator in reply to Judithdalston

The "prime" marks identify where things are attached. If they are attached to the first carbon ring, they will not have prime mark. If they are attached to the second carbon ring, they have a prime.

The numbers count the carbon atoms round the ring.

So, 5' (five-prime) identifies the fifth carbon atom on the second carbon ring.

Levothyroxine is:


It has four iodine atoms - one connected to each of the third and fifth carbon atoms in both the first and second carbon rings.


T3 is:


That is, it has "lost" the 5' iodine atom.


Reverse T3 is:


It has "lost" the 5 iodine atom.


A picture (and more explanation) - though not easy even then:


Thank you... x

Dawid86 profile image
Dawid86 in reply to greygoose

I agree. After months and months on t3 only, from 50 to 80 mcg(last 4months),i have my ft4 0, just now, and still have so high rt3, how is possible..?

Also, last time, 2months ago i had:

FT4 0.17 0.6-1.76, Rt3 1.41 0.10-0.24 ng/ml.


FT4 0, RT3 2.02 0.5-0.95 ng/ml - THEY CHANGED THE RANGE! so wich is the correct interpretation of the actual situation?

Thank you

greygoose profile image
greygoose in reply to Dawid86

It's not that they changed the range, exactly, they changed the machine doing the analysis - or recalibrated it - which gave a new range. You need to use the range associated with the result. And, if you go by percentages, you'll find the results has changed along with the range.

Yes, it is high. And I have no more idea now than I did when you first asked the question. And I doubt anyone else will have, either. We've been through this so many times. But, it still comes down to the fact that… It. Does. Not. Matter.

Why are you so desperate to clear your rT3, anyway? What do you think it's doing to you?

Dawid86 profile image
Dawid86 in reply to greygoose

Thank you, rt3 makes me hypo! It is clear.

Infact using t3 i improved my symptoms and my Adrenals fuction! Also my testosterone total and free, now are top of range.

Mind more clear, better mood, some little energy.

The problem is, last 3 months my rt3 was going down(finally), example ;

2.08 0.10-0.24 ng/ml, 1.72 0.10-0.24 ng/ml, 1.41 0.10-0.24 ng/ml, LAST 4 MONTHS, AND I STARTED TO FEEL BETTER, now my rt3 is 2.02 ng/ml bit with a new range. 0.50-0.95!so i don't know how consider this last value! Because the range.

It is always in ng/ml.

P.s. I have high ferritin, normal iron, suspect inflammation.

greygoose profile image
greygoose in reply to Dawid86

You need to get your CRP tested to see the inflammation.

But, I'm sorry, rT3 does not make you hypo - although raising your T3 will obviously make you feel better, decreasing the rT3, by itself, won't.

You have to consider the latest result according to the range they gave you. It doesn't matter than the range has changed, it's still the same percentage through the range - or above it. You can't chop and change ranges to make your results look better. :D

Dawid86 profile image
Dawid86 in reply to greygoose

Thank you.

My crp is perfect.

Why you say that high rt3 does not make me hypo?

The range has changed but the scale is the same, ng/ml. The range are made on different study, every laboratory can have different ranges.

Infact if you see the ranges in the big study or into an scientific article they consider different ranges like optimal....

For example..

Total testosterone in my laboratory is from 300 to 1500 ng/ml, this range is considered not good for all articles, studies i have read, they consider a good range from 300 to 950 or at last 1100 ng/ml. My total Testosterone before t3 was 600ng/ml,a god not optiamal Testosterone (according to the major clinics etc) , now on 80 mcg t3 i have 1087ng/ml. No one use a range from 300 to 1500ng/ml.

The laboratory said to me they changed the material to run the test, same machine, and they have to write the ranges they look on the new Material they brought to use for their machines... Just this.

So i am very confused!! 😢

Some doctor said me to consider the values and not the new range, if you look at new ranges it is ridiculous;

Old range for rt3 0.10-0.24 ng/ml,

New range 0.50-0.95 ng/ml!

No sense!

Also i just discovers this morning that my ft4 is zero but total t4 is 1.02 ug/dl 5-14,so i still producing t4 that is all converted into rt3.

I should increase my rt3 maybe totaly switch my thyroid.....

I am taking 80mcg,no signs of hyper, still hypo.

greygoose profile image
greygoose in reply to Dawid86

Why you say that high rt3 does not make me hypo?

Because it doesn't. It doesn't make you anything. Poor conversion of T4 to T3 makes you hypo, and the result of poor conversion is high rT3. As you know, there are many, many reasons for high rT3, and only one of them has anything to do with the thyroid. So, there are people with high rT3 who are not hypo.

The laboratory said to me they changed the material to run the test, same machine, and they have to write the ranges they look on the new Material they brought to use for their machines... Just this.

Yes, this is correct. The material they use to analyse the blood is calibrated to a certain range. But, your result will correspond to that range. If you calculate the percentages, you will find they are the same - your old result percentage through the old range and your new result percentage through the new range. It makes perfect sense. Ficticious example:

rT3 0.17 (0.10-0.24) = 50%

rT3 0.725 (0.50-0.95) = 50%

It doesn't matter what the units are, either. You just judge your result by the range used by the machine that analysed your blood.

i still producing t4 that is all converted into rt3.

That is either because you have not fixed the root cause, yet. Or because you are taking too much T3.

I should increase my rt3 maybe totaly switch my thyroid.....

Sorry, no idea what you mean, there.

I am taking 80mcg,no signs of hyper, still hypo.

This is exactly where you are going wrong. While you still have a thyroid that is producing T4, taking too much T3 will cause it all to convert to rT3. Not that this matters in the greater scheme of things, as we've all tried to tell you, but it is your obsession, and therefore matters to you.

But, why do you say you're still hypo? Due to symptoms? Due to FT3 blood test results?

Dawid86 profile image
Dawid86 in reply to greygoose


1- i mean, increasing t3 will switched totally off my thyroid, so my total t4 will be zero and so my rt3 will be zero. At that point, i could take a small t4 in the mix(as tolerated) if needed.

Note: one year ago, i try t4/t3 and my rt3 was higher than no thyroids med, and i was bad. Switching to t3 only, and i using ct3m, increasing very safety the dosage made me "better" for sure.

Before taking any thyroid i had:

Ft3 3.9 1.5-4.1

FT4 0.96 0.6-1.76

Rt3 0.5** 0.10-0.24


2- I know the many root causes for rt3.

My cortisol using ct3m was perfect!

I have normal iron, high ferritin, normal crp. Inflammation? Infections? I don't know.. Any suggestions are accepted.

I was in 3 groups about rt3 problems, or t3only based o Paul's Robinson works, or sttm books.

All people who had high rt3 was much much better using t3only to suppress tsh and clearing rt3 from their sistem, it is a fact! All people! I spoke with thousand...

Also, all people using a good dosage of t3 have cleared their rt3.

They told me i am the first one who don't clear at 80mcg t3.

3- i need t3 for sure, increasing t3, very slow, untill to 75/80mcg gave me improvements. But i feel not good. Also it improved so much my cortisol, testosterone, progesteron, A1bc, mood and some little energy.

Every time i increased t3, from 37mcg to 43, to 50 etc.. I was better in some how. Basically every time i started to feel "worse" at a certain dosage, i was "better"increasing a bit... NOW I AM USING 80mcg FROM 3 MONTHS AND I STARTED TO FELL WORSE IN SOME HOW, also now my ft4 is zero, so i think i need more t3 to compensate in some how the lack for ft4. What do you think?

4-yes i know now i am very high rt3, so i can "tolerated" more t3, infact many people have to reduced a bit their t3 after clearing rt3....

Usually it is safe to stay around 75mcg while clearing, someone prefer go higher.. Also 100, 125mcg but after clearing they will be hyper.

I study a lot, many books etc..

5- Paul Robinson suggested me to increase again t3 safety, they told me, some few patience need 80-100mcg t3 to clear rt3, and he is sure that clearing rt3 will make a big difference.

6- about the new range of rt3.

They brought the material from another builder, the range are decided observing a group of people, so they are not equal always!

Every laboratory could use different ranges.. But..

Let me explain :

I always Runned free testosterone in the same laboratory fro months, okay, my free test was always 26pg/ml! But until last month the range was 8-30, this month it was changed to 15-45,but i have the same values 26pg/ml! From month.

So, the macchie is the same! They only changed the material to use for the test, copying the range that is written on this.

So i am confused!

greygoose profile image
greygoose in reply to Dawid86

I know you're confused, and I don't know how to help you. You believe all the old myths about rT3, and people have tried so hard to explain to you that they're not true.

I do not doubt that you need to take high doses of T3 to feel well. I, myself, take 75 mcg. That is my dose. I've experimented with higher and lower dose, and that is the dose I need. You have to find the dose that you need, of course you do. But, life would be so much easier for you if you could just drop this obsession with rT3. It is irrelevant. It is inert. It is out of the body in about two hours. And, if your cause of rT3 is non-thyroidal, the T3 is not going to get rid of it. I don't care what anybody on Facebook says. I have seen some of the rubbish they spout on Facebook on the various groups. You'll get much more reliable information on here.

So, my advice to you would be to drop Facebook, forget about rT3 and concentrate on optimising your FT3, your nutrients, cortisol and sex hormones.

As for the ranges, I would suggest writing a new question, asking just about that. Then someone who explains things better than me can explain it properly. :)

Dawid86 profile image
Dawid86 in reply to greygoose

Thank you.

You said me, I can tollerate more t3 due the fact i have high rt3.

Rt3 is brake for metabolism.


So considering the new range my rt3 is lowering from 4months.

And this is a confirm that using enough t3 so suppress tsh 24/h,help to clear the rt3 from the sistem, clearing the t4. No t4 no rt3.

It seems logical to me.

It normal using more than 80mcg t3? Do you know males who need more than 75mcg?I am on 80mcg, my bp seems little lower than the past month, now 109-112/75-80, hr 77-85. Temps from 36.6-37.1 at afternoon.

Taking t3 25mcg@4:00am,32.5@10:00am,25@4:00pm.

Waking 8.30/9am.

Now my cortisol is ok.

But still feel very tired all day.

Sex Hormones are okay.

greygoose profile image
greygoose in reply to Dawid86

You said me, I can tollerate more t3 due the fact i have high rt3.

I really don't think I did say that. It doesn't make any sense.

And this is a confirm that using enough t3 so suppress tsh 24/h,help to clear the rt3 from the sistem, clearing the t4. No t4 no rt3.

It's been explained to you that suppressing the TSH doesn't not stop the thyroid producing hormone, it just slows it down. And, of course, the less T4 you have, the less rT3 you have, but it doesn't mean you've solved the problem.

It normal using more than 80mcg t3? Do you know males who need more than 75mcg?

I don't know any males on T3 only. But, I know some women that take more than that - quite a bit more. You need what you need.

greygoose profile image
greygoose in reply to Dawid86

Rt3 is brake for metabolism.

rT3 does slow the body down, yes. That does not mean that it 'blocks the action of T3'.

If you have a normal working thyroid, or are on T4 only, and then go down with the flu, or something, more T4 will be converted to rT3 than to T3, which is a perfectly normal process, giving the body time to rest and recover. This is due to the conversion process, nothing to do with the actual rT3.

But, if you are taking T3, the rT3 will not have any effect on that T3. Metabolism will not be reduced because you will still have the T3 you are taking.

Hope that makes sense. :)

As I said, if you have a thyroid, you can still make T4 which will convert into rT3 if you system thinks it needs to be slowed down. I'd try reducing your T3 dose and see if your rT3 comes down. The only way to remove rT3 completely is to get your thyroid removed and take T3 only - but I don;'t suggest that is good thing to do. I think you are getting side tracked by the wrong thing

If i take less t3 i feel more hypo.... I started to feel better at 75mcg t3! But just 31mcg t3 make my rt3 over range.

The point is I discovered i didn't have high rt3 before any treatment, the laboratory gave a me A WRONG RANGE FOR 1 YEAR!! THEY SAID ME IT NOW!! INCREDIBILE.

My rt3 1 year ago was

0.54 0.50-0.95.

Using t3 improved some symptoms much better that taking 50t4/20t3 or 50 t4/25 t3, i tried it for a month, also taking 50t4/19t3 I had an over range rt3..... And i felt more hypo than using for example 37mcg t3 only. This is a fact.

Increasing slowly my t3 to 37,43,50 made me little better, than after 1month on 50mcg I started to fell worse again, so increased to 56,than 62mcg and fell better..than I increased to 68,75,80 and felt better.

Now i was 3 month on 80mcg, first 2 months like 25mcg,25mcg,25mcg,6.25mcg at evening - started to fell more hypo after a month on this!

Now last month i am taking

25@4am (ct3m), 32.5@10am, 25@4pm...i sleep little better, but waking worse and in general infell worse, more hypo than the first month on 80mcg with the first schedule i wrote above.

So, i don't know what to do.

I have some headache at later afternoon /evening i didn't have last months!

I feel more tired, less motivated..

Only change is now my ft4 is zero, but i have a little little ammount of total t4.

Untill 2months ago when i was better, i have a little ammount of ft4 in my sistem.

So now why I feel worse?

Need more t3 again? Or less?

I feel worse when my free T4 drops below range. I feel better with it at the bottom of the range. Got rT3 done once, years ago and it was mid-range. Don't get it done now. Sorry, can't really help - it seems to be a very individual thing - I take my T3 every 6 hours. I get headaches if I forget to take my sex hormones or magnesium. But there are plenty of people here on T3 only who know a lot more than I do.

You wouldn't necessarily expect to have low rT3 unless you haven't got a thyroid. Overmedication with T4 is only one cause of high rT3. Chronic illness, dieting, over exercising, stress and too much T3 also cause high rT3. It is usually a red herring as it is pretty much impossible to know what the cause is unless you *know* you have a serious chronic illness. As you've discovered, not taking T4 doesn't change it unless that was the root cause. rT3 is not a problem in itself - it doesn't block T3 receptors; it is converted to T2 and then to T1 pretty fast and then eliminated - the cause of the high rT3 is the problem, but you need to find out what that is (almost impossible).

It is not correct.

With no t4 on your sistem, you CAN'T HAVE RT3! Because it is made from t4 only!

Rt3 is potent metabolism inhibitor abd block the effect of t3.

This is a fact.

Not a fact as you state it, If you have a thyroid, it can still make some t4 which can be converted into rT3 - even 100% of it to rT3. What you say is partly true if thyroid has been removed. But rT3 does not block the action of T3 at all, as has been proved in recent studies, It used to be thought that it did but now we know it has its own receptors. Trouble is, a lot of info on the web has not been updated in many years to reflect more up-to-date research. You can see it's not true from the blood results (where do you think the rT3 comes from - the fairies?), But so what? It doesn't stop your T3 from working, and it's possible that T2 is even more important than T3 for things like weight management and that's what happens to rT3.

If your thyroid is totally switched off, with a tsh suppressed 24/h,you haven't t4 in your sistem so you can't have rt3.

Rt3 has its receptor, but it is a potent metanolo blocker, infact itbis used from the body to make slow the metabolism in particular situations, when you need to conserve energy!! It is a fact.

I know thousand of people who are well only clearing their rt3. Also Paul Robinson, who wrote 3 books.

I don't want to discuss about the role of rt3, but i want to have some feedback or idea about my situation.. Just This.

I can't tollerare t4!! And feel better on t3 only for sure.

You said yourself that you are still producing a decent amount of T4 (total T4) and it looks as though all that is being converted to rT3 as you are probably taking too much T3 or you have another "need" for rT3. You keep disproving your own arguments with blood results and then refusing to acknowledge it. I suggest that you just get on with it on your own until you feel better or worse, since you don't what to listen to anything anyone suggests here. You've already made up your mind and just want someone to tell you are right (you might find people who will say that on STTM), so I don't really understand why you asking. No idea what metanolo is, so no idea what might inhibit it. I take T3 only but I still have rT3. BTW ideally your CRP should be under 1.

Thank you.

Are you taking t3 only, what is your rt3 values and range? I am curious.

Wich is your t3 dosing?

Are you feeling well?

Why are you on t3 only?


So, according nn to this fact before to start any thyroids my rt3 was perfectly in range!! Not high.

Of course, i know that letting some t4 in my sistem and taking t3 only is making higher my rt3. Now i am taking 80mcg t3 and I have Rt3 2.08 0.50-0.95 ng/ml, when i took 31mcg I had Rt3 1.7 0.50-0.95, so also just 31 mcg make my rt3 high.


Rt3 is a potent metabolism blocker* not metanolo.. 😅

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