Thyroid UK
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Advise on (sadly but hopefully temporarily) returning to T4 from T3

Has anybody experience of returning to T4 from T3 treatment?

I have been following Paul Robinson's protocol and have been using CT3M since 18th July. I have had periods of time where I felt great but have had some really rough patches and am going through a particularly difficult time now. I am struggling emotionally and anxiety is at an all time high, symptoms are affecting daily family life and my job is suffering. My HR is consistently elevated (and spikes over 100 at times), I have also been getting regular temperature spikes, my temp for the last three days has remained high all day and this afternoon spiked to 37.7 even though I have reduced my dose.

I've been dosing for several weeks 18 @ 5am, 12.5 @ 11am and 12.5 @5pm. I have only had one day of feeling good in all that time (either at ovulation or just after).

Yesterday I dropped the 3rd dose to 6, had a fretful night and woke with a temp of 37C.

Today I dropped the 2nd dose to 6 and don't think I should take a third dose at all.

It feels like a massive decision to stop the T3 but I can't carry on as I am.

I am sure there are other factors at play, blocking the T3 from working and am in the process of getting them investigated. I am privately getting a second adrenal test done, a sex hormones test and am going to ask my doctor to test for aldosterone. I'm hoping at some point I can return to T3 only as have the faulty DI02 gene and T4 wasn't working for me, but overall I was better than I currently am! I have Hashimotos.

I have been advised to stop T3 for 24 hours, to then introduce thyroxine at 25- 50% of my previous dose - I was on 200mcg. I have also had the same advise from my doctor, she advised starting at 100mcg. I'll then hold this for several weeks and keep an eye on symptoms. I would like to try adding some T3 to the T4 but won't do this for several weeks.


How was the transition for you?

Did you feel much worse?

How long will the T4 take to kick in?

What do I do if hyper symptoms continue?

Thanks for reading and any help and advise gratefully received.

29 Replies

CharliesCat, I think you're probably undermedicated on 43mcg T3 which is equivalent to 129mcg Levothyroxine (T4). 200mcg T4 is equivalent to 67mcg T3. If you are a poor converter you need T4+T3.

I don't see why you need to start T4 on a lower dose than you were previously used to unless you were overmedicated. When I stopped T4 for RAI the 150mcg dose was reinstated 5 weeks later.

I didn't do at all well when I was switched from T3 to T4, and had problems tolerating T4. Adding T3 calmed the adverse effects and improved low FT3 due to poor conversion.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thanks Clutter. I am showing all the signs of being over medicated, whether it's that or other issues are factor meaning that I can't tolerate anymore at the moment.

I've skipped my last dose today to see what my body does...


CharliesCat, have you had FT3 tested to see whether you are overmedicated?


Due a blood test but not until December. Lab through my GP also make their own mind up as to whether they test it! Could look at getting it done privately.


CharliesCat, could be worth it. You could address over or undermedication without switching back to T4 then if you wanted to.


I agree. I am really reluctant to go back to T4. However the last few days have been so bad, I am barely functioning.


dosing t3 is by symptoms, not tests! They don't tell anything if you have thyroid hormone resistance! When you have hyper symptoms you lower the dose every 3 days or so. If you were able to tolerate 200 ..maybe i read wrong..and not die, you must be resistant.


Yes I am resistant and know that TSH, T3 and T4 tests are redundant now on T3. The problem at the moment is there is much confusion as to what are adrenal and what are thyroid symptoms. I'll admit I have lost confidence in dosing by signs and symptoms as there is so much cross over!

My temp is still high even though I've reduced. My HR spikes when due a dose, when on too high a dose and when I get adrenaline surges. My BP is fluctuating. Today my BP has been low all day but with a fast HR….


Do you have hashi's? It could be a flare sure sounds like it. The thyroid tests aren't going to do you any good. Maybe consider an autoimmune protocol, to put hashi's in remission, by healing your Gut. I signed up for Dr. Isabella Wentz's emails and got a functional medicine doctor. I have been where you are before.


Is 5 am maybe too early for the first dose. Maybe try a bit later. I did read the book a while ago and think the first dose should be later if you felt overdosed.

Someone please correct me if I am wrong

Jo xx


Hi Jo. To start with I've tried reducing. Dr Myhill also advises as close to 5am but I will try later after a few days. As far as I understand why can happen is the dose can supercharge the doses for the rest of the day or too much cortisol can be produced.

It is all so confusing!


There was a doctor who used T3 for himself and also for his patients who were Thyroid Hormone Resistant. His advice (which I follow) is invaluable and before you give up on T3 maybe try the following. Excerpt:

Third, the leaflet on Cytomel pharmacies give patients when they fill their prescriptions states, "POSSIBLE SIDE EFFECTS: NO COMMON SIDE EFFECTS HAVE BEEN REPORTED with proper use of this medication." This information is accurate—when plain, full-strength, one-time-per-day doses of T3 are used properly, there are no adverse effects. The only adverse effects occur when a patient takes a dosage that for her is excessive. With Cytomel, if overstimulation occurs, it can be stopped with one or two small doses of propranolol. Or the patient can simply reduce her dosage of Cytomel the next time she takes it. I want to emphasize, however, that when our protocol is used properly, there is no overstimulation to be avoided by using timed-release T3. The protocol has safeguards against adverse effects.

And finally, why do I specify that the typical patient use one full dose of non-timed-release Cytomel for life? Because extensive testing has shown that this is safe, effective, and most economical—when used within the context of our entire protocol.


Rather than being a hormone, T4 is a “prohormone.” That means that enzymes have to convert T4 to T3 before T4 benefits us. T4 is no more a hormone than beans in an unopened can are a food. For all practical purposes, canned beans become food only when a can opener frees them so you can eat them. Hence, T4, like canned beans, only potentially benefits us, but actually does so only after being freed from its metabolically unusable form.

Your endocrinologist may say that T4 is a gentler way to get T3 into your body. This to me, however, is a specious argument. When taken properly, T3 can effect one as gently as T3 derived from T4.

I take T3 only once daily and am well. Dr Lowe said elsewhere that T3 (active hormone) has to saturate our receptor cells and then the work begins which lasts between one to three days.


Hi Shaws. I've read a lot before about single dosing and it did seem to make sense to me, but I'll be honest, I am wary after some of the thing's I've read in Paul's books - not that I can recall that information right now!

I am not keen at all on returning to the T4 but at the moment it feels like a known quantity.

I am definitely showing signs of hyper, so I am scared to try a single dose. But is that because my own thyroid is now kicking in, I don't know?!


After my experience with levo with pulse rates at 150+ and being so unwell. T3 was/is a saviour for me. Dr Lowe took 150mcg of T3 once daily.

As soon as I took T3 my whole system calmed down particular my heart which used to take off day/night anytime and was more often in the A&E wondering what was happening to me.

I take about 1.5 tablets daily. I've never read Paul's book but I do know his procedure works for him but not for everyone.

I much prefer once daily dosing of whatever I've taken, NDT etc. I have a life - take T3 when I awake and vitamins/etc at lunchtime. I am well and have energy and a calm heart.

There are also misinterpretations of T3 ie. that it peaks quickly etc.etc. It does go into your bloodstream quickly but it then goes into our receptor cells and then the 'effect' of that one dose lasts between one to three days. I've even missed one day's dose and had no ill-effects.

Of course, everyone has to make their own decision but how were you previously on T4.

1 like

You do make it sound very appealing. To be honest it is hard to remember here is a list from notes; very low mood, fatigued, hair loss, brain fog, dry skin, mood swings. Blood tests all normal (!) of course but T3 very low in range.

I wasn't that bad (as you describe your experience, that was more how I felt before diagnosed) but felt like there was plenty of room for improvement. No anxiety, like at the moment.

I am currently taking Tiromel as was getting bloating on NHS Lio. How would I go about trialling a single dose?


What dose of levothyroxine were you taking?


I'd got up to 200



I think the Paul Robinson method is excellent to get thyroid hormones working when adrenals are shot as when cortisol is very low ( or high) ... no thyroid hormone replacement will work well.

I haven't tried the CT3M method but was medicating T4 & T3 divided into two doses a day. Now I have my adrenals working "Ok - ish " , I have dosed T3 once a day as per shaws and it is working really well. I continue to have more energy and get better (albeit very very slowly) each week.

You are wise to get a second adrenal test done, a sex hormones test and aldosterone tested as any of these could block the T3 conversion.

I have the faulty DI02 gene and have had ALL these tested and also thyroid antibodies (which are still high ...arghhh ! ! ) .. but my thyroid hormones are building and that's the main aim.

Don't forget optimal nutrients n everything and supplement selenium and such like to aid conversion. Also good diet as thyroid hormones love fats and carbs...

Good luck,



Disclaimer: I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.



Thanks Flower. Yep, have a very healthy diet and taking lots of supplements, much to the detriment of my bank balance.


25mcg of T3 is equal, in effect, between 75mcg and 100mcg.

I would make a note of my basal temp test first thing before getting out of bed plus pulse - as well as normal temp/pulse a couple of times during the day just to keep an eye on them. Sometimes we feel hot and might think we taken too much but if temp/pulse temp hasn't changed you've not overdosed. 1 1/2 tablets to start (if 25mcg) and after two weeks add 1/4 and after another two weeks another 1/4 or you might feel fine on 1 3/4. Any sign of overstimulation drop back one dose.

Read the whole link I gave above for information.

"I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions"

1 like

shaws what is low free t3 in range? what should it be ideally numberwise?


Labs differ in their ranges so a low free T3 would be at the bottom of the range or lower than the range. To feel best our T3 should be towards the upper half of the range.


I also took just a single dose of cytomel every morning for over 30 years with absolutely no ill effects ever. I always felt good, I was in good health and excellent shape. My doctor retired and I had to find a new one who put me on a combination of T3 and T4. He reduced the amount of T3 and told me to take it twice a day instead of once. I want my old doctor back.


More importantly, you also want your health back. I'd go back to the dose you were well on. They cannot dictate what may be keeping us unwell plus there is also a danger we might develop other more serious illness due to being under-dosed. Before blood test were introduced the normal doses of NDT were between 200 and 400mcg daily.


Just reading the links now. I have read them before but will try to take the info in as best I can!


Yes. Perhaps I am letting the temperature guide me too much. However my pulse is erratic, as is my blood pressure.

Thanks all. The single dose is definitely something to consider trying.


Why not just lower the dose and take it like a person normally would. Your symptoms are of overdose!


I mean, lower the dose from 200mcgs. It takes several days, up to 1 week, for a dose decrease to fully kick in. I fear if you are doing 43, it was a huge drop and too low. Who told you to go back on t4?


Don't forget a spiking and persistently high temperature could also mean an infection, causing a fever! If it hasn't sorted itself out by now, 9 days after your post, you need to see your doctor - call him/her in! Hopefully you are feeling much better by now. -:)


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