Thyroid UK
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Levothyroxine (T4) and Liothyronine (T3)

Hello all....

I was taking 175mcg of Levothyroxine but on request, my consultant reduced the Levo and wrote to my GP requesting Liothyronine to be given to me. I had a total thyroidectomy approx. 10 years ago.

The consultant recommended 100mcg Levo and 20mcg Liothyronine but my GP was reluctant to prescribe 100mcg and reduced it to 75mcg instead. Does anyone know which recommendation equates the closest to the original dose of 175mcg Levo?

Thank you :-)

7 Replies

It is impossible to calculate exactly how much T4 is equivalent to an amount of T3. So there is always a certain amount of seeing how it goes. But for a rough idea, people often assume you need four times as much T4 as T3.

So, your consultant saying 20 mcg of T3 - so drop T4 by 75 is reasonable.

Some people suggest it should be five times as much T4 as T3. Which would make your GP reasonable.

It it were me, I think I would go with consultant's view if I could choose. GP's view is, I suspect, over-cautious so could result in underdosing.

Others may have their own experiences to add - I do NOT take T3.



Thank you for replying.... :-)

I have just had some blood tests done which will be forwarded to my consultant before I see him again at the end of the month. These include free T3 tests and other things that he wanted to see.

I still feel sluggish, which is why I asked but also have a large fibroid in my womb (another issue!!), so it may be because of that.... difficult to say. I haven't lost any weight on Liothyronine.... in fact I've gained some!! So annoying.... and I still have aches down the front of my leg shins but less brain fog.

I'll see what the blood tests throw up and suggest that the endo. increases the Lio for me, I think.


Thanks for clearing that up i didnt kno about the T3 and T4 tablets and the difference between them.

@ marbez i get that brain fog all the time too.


I didn't know the difference either until I joined this site.... it's been a huge learning curve for me. Sometimes I think this thyroid illness is turning me into a recluse! I've no energy to socialise after work..... in fact, all I do is work, eat and sleep and people just don't get it when I keep saying how tired I feel.


@marbez i got threw off my work as my condition got worse and all i do is sleep - sometimes i am too tired to eat and just sleep all day sleep 12 hours straight then get up take my meds and by that time i have to go back to bed or if i try and go out i have to go right to bed again - yes welcome to the world with no social life and no normal people that dont have this condition dont understand or think your lying or maybe think you're anti-social as they really dont have a clue what it is like living with this condition.


That's not good ^^^ Please go back to your GP and get some answers, as this is no way to live. I am slowly getting mine sorted but it has taken time to get someone to listen to me. At my last endo. appt., I went with a notepad of things so I wouldn't forget and a lot of knowledge from this site. That's the only reason I was given Liothyronine.... had never heard of it before coming on here.


Just received a letter from my GP this morning asking me to go in.... which confirms that something isn't right and they will probably now increase my dose of Levo.

I'm starting to get quite good at reading my own symptoms now.... :-)


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