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Thyroid UK
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T3 only

After a year of intermittent misery on T4, I weaned myself off and felt so much better on nothing - just like my old self. However my consultant has now prescribed T3 only, starting on 5 mcg per day. I am only on day two and am already feeling lousy. Would love to hear from anyone else on T3 and hear how long it took to feel ok.

Many thanks

13 Replies


Can you post your recent thyroid results and ranges (the figures in brackets after results) to help members advise?

It takes 48-72 hours for T3 to enter the cells before it will start to work. 5mcg T3 is a tiny dose so may not be very effective.


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.


I swapped from T4 (years) to T3 after a period on nothing. Nearly died on T4. Felt great on nothing until the hypo symptoms kicked in and I started sleeping all the time and my TSH was 98.

5 mcg is a tiny dose. I was on 100mcg T4. The endo prescribed 10mcg for a month then 20 mcg for 2 months then 30 mcg for 2 months then 40 mcg four months later. He refuses to up mine anymore because of my low TSH (0.07) even though my T3 isn't high at 3.8.

Lifestyle changes have done me lots of good too. Gluten free, pilates (I couldn't even have dreamt of doing pilates on T4 or nothing). I stopped feeling sleepy tired fairly quickly (days, weeks). I take my T3 very early in the morning (6 or earlier) then go back to sleep for a while.


Thanks so much for your reply - that is all very helpful. When I was put on T4 initially my GP started me on 100 mcg which nearly killed me. I think my endo is aware of this so is starting me off v slowly. My recent TSH was 13.9 so not so high.

Am v hopeful this will work. I definitely do not want to go back on to T4 as felt really ill for ages.

By the way I assume you have to pay for your T 3 ?

NHS rules that only T4 can be prescribed as far as I can see.


No. Prescribed by an NHS endo on repeat from my GP practice for nearly two years now. So far they have not refused my prescription - despite their CCG guidelines ("Joint Formulary") which I don't think I technically fulfil. But I have proved, and the endo agrees, that I cannot tolerate T4 so unless they want me comatose then T3 it is. Sadly for them, they have improved my health to such an extent that they would have a very large fight on their hands if they tried to change it.


Lucky you. My GP won't contemplate it so I am going to have to fund whatever it costs privately.


If the endo is an NHS endo and prescribes it for you I don't see how the GP can refuse. I will pm you a spreadsheet that I got from this site. It lists all the NDT and liothyronine prescriptions by CCG and practice in the country. It may be useful. I'd link it to the post I got it from but can't find the post and wouldn't know how to link it.


Thanks - that would be brilliant.

1 like

By the way do you have any side effects with T3? I have only just started on it but have a terrible headache at the back of my head and up my neck.

Do you know if it is ok to take Paracetamol Plus with T3?

Many thanks. Any advice welcome ...


No. I had no negative side effects at all. I try to avoid all medicines because unless absolutely necessary I see them do more harm than good. Clearly the occasional painkiller should be ok. Ibuprofen works better for me for headaches. I'd recommend a bath with almond oil and some drops of lavender oil.


Thanks so much for your reply. I took paracetamol plus which got rid of my headache but somehow gave me terrible indigestion which kept me awake all night!

Wish I could steer clear of all pills. I felt so much better when taking nothing.


What dose of T4 were you on before taking yourself off it?

5mcg T3 is roughly equivalent to 15mcg T4.


I was on 50 mcg T 4 but felt awful. My endo wants to start me slowly with T 3 and work up as required.

Fingers crossed this works

Thanks for your reply.


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