Equivalence between Liothyronine and Levothyroxine doses??

[Caradoc1a]

Please can someone point me to where I can find this info? Thank you so much. I think I might need to up T4 and reduce T3 soon. No point asking Endo as there's no appointments available for 56 weeks! 🙏🙏

[GlowCoach Administrator]

There really isnt an exact equivalence as it will depend on how each individual absorbs each hormone and how the body uses and converts the T4. Therefore, blood results should always be a guide.

[Caradoc1a in reply to GlowCoach]

Thanks! I did wonder if I was deluding myself bu thinking it would be simple!! 🙄🫤🤷‍♀️

[greygoose]

I can understand the need to up your levo, but why do you think you may need to reduce your T3? It's not automatic and you can change one without having to adjust the other.

[Caradoc1a in reply to greygoose]

Thanks for replying. I think I might be a good T4 to T3 converter as upping T4 from 25 to 37.5mcg resulted in T4 increase of 7.2 to 7.3. At the same time T3 changed from 3.9 to 5.6. I'm now upping T4 to 50/37.5 alternate days. I'm worried about too much T3. I'll do blood tests in 8 weeks.

[greygoose in reply to Caradoc1a]

Such a small increase in of the FT4 could not possibly result in such a huge increase in the FT3 - you'd be converting T4 you do not have!

However much T4 you take, only 30% of it is ever converted to T3, maximum. And if you're a poor converter, it would be a lot less. I should think you have a long way to go before you have too much T3 unless you increase your lio.

[Caradoc1a in reply to greygoose]

I forgot to say that I take 20mcg Lio per day as well (since June 24). This has been constant and so can't account for the recent rise in T3 - I don't think so anyway!!

[greygoose in reply to Caradoc1a]

No, I doubt it. Do you have Hashi's?

[Caradoc1a in reply to greygoose]

No - was hyper for years and then had RAI

[greygoose in reply to Caradoc1a]

OK, so it wasn't that.

So for that particular test, how long was the gap between your last dose of T3 and the blood draw.

[helvella Administrator]

I wrote a blog intending to explain the equivalence issues but it is, I think, very difficult to explain in a few words.

I'm in the process of re-writing/reformatting in an attempt to improve it!

helvella - How much more potent is T3?

A discussion about the relative potency of T4 and T3.

Last updated 10/02/2025

Link to blog:

helvella.blogspot.com/p/hel...

[Caradoc1a in reply to helvella]

Thank you!