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.

[Caradoc1a in reply to greygoose]

12 hours before. The test was 8.40am and I took 10mcg at 8.30pm the night before. I started B12 injections EOD 22nd Dec. That's only other variable I can think of.

[greygoose in reply to Caradoc1a]

Pretty sure the injections wouldn't have had anything to do with it. But, then again, I'm equally sure that it had nothing to do with conversion improving. So, be very careful how you alter your dose. You don't want to find yourself under-medicated on T3.

[Caradoc1a in reply to greygoose]

Thank you! I'm seeing GP on Thursday and will have a chat about agreeing to test FT3 and FT4 in 8 weeks and supply T3 tablets instead of capsules. If they won't, I'll test privately. I think I'm going to have to experiment with doses because, as far as I'm aware, my FT4 needs to be higher than 7.3 even though FT3 is 70% through the range. I am feeling much improved this week since upping T4.

[greygoose in reply to Caradoc1a]

Even if the doctor does request the FT3, the lab can refuse to do it, I'm afraid. But doesn't hurt to ask.

'Experimenting' with doses sounds a bit drastic. What you need to do is very slowly increase your levo, leaving your T3 where it is, until you feel well. A lot of people need it quite high in range, even though their FT3 is good.

[Caradoc1a in reply to greygoose]

Thanks - I didn't mean to sound so cavalier!! I will only increase by 12.5mcg each time and wait for 6-8 weeks and test. I will leave T3 alone till I have more evidence of how T4 is affecting it. At that point I could see a good private Endo to gain specialist advice. Plus keep up with vits and minerals. I'm just a tad worried about an over the range T3 due to the stuff I've read about high FT3 leading to bone deterioration as I have osteoporosis. I need to do more research into that aspect.

Thank you for your support 💐💐💐💐

[greygoose in reply to Caradoc1a]

Just going briefly over-range on your FT3 is not going to have an instant effect on your bones. It takes years. So if you test after six weeks and your FT3 is slightly over-range - it's not going to be at dangerous levels, I'm pretty sure of that - then you just reduce your dose slightly, no harm done. To cause or exacerbate osteoporosis it would have to be very high, long term.

Remember, ranges are only a rough guide to the levels most people have, not the level you should aim for or that would be right for you as an individual. The upper limit is not a stone wall that you can't cross - a lot of people need it over-range to be well. So, don't get too hung up on ranges- remember, doctors totally ignore them when it suits them, so they can't be that important!

[Caradoc1a in reply to greygoose]

Thank you. Wise words

[greygoose in reply to Caradoc1a]

You're welcome.

[helvella]

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!