Will adding T4 push my T3 too high?: At last! I... - Thyroid UK

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Will adding T4 push my T3 too high?


At last! I think I might be getting the hang of this (she dared to say very quietly 🤣)

Short history: started on 10mcg T3/125mcg levo in March. Initial bloods looked good after 4 weeks, felt great.

Shortly after symptoms returned, so increased by 5mcg T3/ day and repeated each time symptoms came back until about 6 weeks ago when I stuck at 25mcg T3/125 levo per day.

Symptoms returned again about three weeks ago (it’s the muscle weakness for me) and as of last week my thyroid became a bit swollen which is a dead cert for low T4 for me. I suspected this might be happening anyway if I’m honest as I know T3 pushes T4 down.

So, my intention was to increase levo to 150mcg again. I’d this too much? (175 was pretty standard for me prior to my issues). Will it push my T3 too high? Am I best just to only change the levo and wait to see if I feel overmedicated?

Also for the first time over the last two days, I’ve noticed my T3 making a difference in the afternoon. As in, it doesn’t clear the muscle weakness but it helps about half an hour after my afternoon dose. Prior to this week, I’d have said it made no difference splitting the dose although I’ve always done this up until now. This has thrown me a wee bit - does that mean I need more? Surely not.

I’m slightly worried about the low TSH. I’m mean, I'm not but the endo mentioned it last time (and it was marginally better), so I know it’ll pop up in any conversation with and doc! Should I bother about it?

Anyway, results attached. Just for reference when I was on 150 mcg levo, my FT4 was around 20 on the same scale as these results. 😊

15 Replies

We have to give increases in dose a chance i.e. to be absorbed to optimum before we make assessments that we're on too much or too little. The best way to judge is 'how we feel'. Are our symptoms resolved/resolving? TSH can be low or very low if we take or add T3 to our dose of T4. This is because the blood tests were introduced for levothyroxine (T4) alone and I know this makes Endos/doctors nervous as they make the assumption we've gone 'hyPERthyroid. If we add or take T3 or NDT results cannot correlate but it is always how the patient 'feels' on particular dose/hormones.


The following link may be helpful. It is by one of Thyroiduk's Advisers (now deceased). He'd only take one blood test for the initial diagnosis and thereafter it was all about relief of clinical symptoms. He'd never prescribe T4 (levo) only NDT or T3.


Murphysmum in reply to shaws

Thank you.

Yes, I’ve personally been disregarding TSH for a while now, just sometimes you doubt yourself! It’s good to be reminded though 😊

But, what was your FT3 when you were on 150 mcg levo? Whether or not increasing your levo sends your FT3 over the top depends on how well you convert. And, none of us can guess that. I think you're just going to have to try it and see what happens.

Your TSH is low because you don't need it. TSH has two jobs (and only two, no matter what your endo tells you). It stimulates the thyroid to make more hormone. Now, it doesn't need to do that because you're taking plenty of exogenous hormone, and your thyroid wouldn't be able to respond, anyway, because you're hypo. Secondly, it stimulates conversion. And, you don't need it to do that either since you're taking T3 - and, apparently it was very good at that, anyway, which is why you needed to take T3. And that's it. The pituitary has detected plenty of thyroid hormone in your blood, so have cut back on TSH production. And, the only way to raise it is to reduce your thyroid hormone replacement and make yourself ill. We all know this, such a pity that doctors don't. :)

Murphysmum in reply to greygoose

Thanks @greygoose, I’m finding it hard to totally disregard TSH but I am determined to do so!!

I just need to memorise that part of your reply to regurgitate to any medics I may come across.

I’ll have to go and look back to know for sure but my T3 was never disastrous. It was always within range and I do recall that my T3 went up to the top of its range when I was on 200mcg levo. My FT4 was way over range at 30 😱 and I felt overmedicated.

It’s almost like I need the actual T3, separately, to make me feel well though I know that’s ridiculous!

I know I’ve got room to increase levo, and obviously didn’t convert well (if not badly) so hoping I might be able to increase ok, then maybe reduce T3 by 5mcg afterwards.

I’ll look for those results....

greygoose in reply to Murphysmum

It’s almost like I need the actual T3, separately, to make me feel well though I know that’s ridiculous!

I'm not sure what you mean, there. You are taking T3 separately. That's what a lot of people do.

So it sounds like you don't convert at all well. In which case, try increasing the levo, and see what happens. You can always reduce it again if it doesn't help.

But, I wouldn't reduce the T3, if I were you. :)

Murphysmum in reply to greygoose

Thinking about it, I don’t have FT3 bloods on 150mcg. Well, they would have been done a long while back by the go, so they wouldn’t have done T3.

I only have results on 175mcg and then it was 4.61 (same range)

I think I may increase the levo and see how I feel before maybe dropping T3 🤷🏼‍♀️

greygoose in reply to Murphysmum

Absolutely. You don't want to reduce your T3 unless you absolutely have to. :)

Why don’t you try cutting 5mcg of T3 and adding another 25 of Levo? It is after all trial and error for all of this.

Murphysmum in reply to NWA6

Hmmm. Agreed but I think I’ll just top up the levo for now.

I personally think I’ve still got room for a slight increase in T3.... not in the ranges but I just feel I could manage it.

So I think I’ll stick and see how the levo impacts it. Espectsimce ive just read that Paul Robinson post about ignoring ranges! 😜

NWA6 in reply to Murphysmum

Fab! It feels good when you set your mind on a clear way forward. It’ll work or it won’t but it’s all relevant 🤗

Murphysmum in reply to NWA6

Indeed! I really feel like I’m getting there now. My optimism could be dashed of course if what I expect doesn’t happen when I increase levo but hey, I just repeat the process.

I feel so much better in charge of my own destiny though.

Now to add some fitness to the regime 😬!

NWA6 in reply to Murphysmum

Ah sure the fitness will come. I’m only just starting back to fitness now, it’s been 3mths of stability for me (although I’m beginning to think my FT4 might be slightly too low now) and only now am I starting healthier habits. I’ve just been enjoying my life after soooo long of being unwell.

Your current dose is very very similar to mine !

I take 125 T4 + 12.5 T3.

Can you please post your previous FT4, FT3 and TSH before your started taking T4 + T3?


Murphysmum in reply to Blueskyyy

My previous FT4 was way over range so not really applicable. I think when I was on 175mcg levo (which was more the norm before we started trialling things), my FT4 was around 20 (12-22), FT3 was 4.6 (3.10-6.80) and TSH has always been low, it was 0.3 (0.27-4.20) 😉

I think its completely reasonable to try adding in some T4 if you feel like it might help. You can always wait 6 weeks or so, and if you don't feel an improvement change it back.

I'd say it's a slightly unconventional thing to do, becasue T4 in itself probably doesn't do anything much. But there are definitely some people who feel they need it at a certain level to feel well.

My experience with split dosing has been that it didn't seem to matter when I was undermedicated. But at some point as I increased my dose I was noticeably less well at certain parts of the day (I say noticeable, but still always tricky to tell with thyroid symptoms), so I started splitting my dose to give me a boost at those times. Since then I've juggled the doses and how large each one is many times to keep things quite smooth across the day.

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