Thyroid UK
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Inconsistent results

In October 2015 I was taking 37.5/25 (i.e. levothyroxine/liothyronine). Results were TSH: 0.24; FT4 7.33; FT3 5.0. For some forgotten reason I moved away from that dose to 75/25 in October 2016. Then the results were TSH: 0.02; FT4 12.9; FT3 4.0. Ranges TSH [0.27-4.2]; FT4 [12-22]; FT3 [3.1-6.8]

Does change in results make sense? So lower levo (37.5) leads to higher FT3 (5.0) compared with 75T4 and FT3 of 4.0.

I am going demented trying to get the right combo of meds, results and symptoms.

Can anyone shed light on these apparent inconsistencies? I can think of a couple of possible culprits but don't want to put ideas in anyone's head!

Many thanks.

16 Replies

I don't think increasing the T4 would lower the FT3. Did you have both tests done at the same time of day?

Could just be that your thyroid is getting worse and you need more T3. Why did you increase your T4, anyway? Myself, I would have increased the T3.

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Don't ask me why I increased T4! Who knows?? I do try to get all thyroid tests done at roughly the same time of day, yes, and before taking the meds.

For the last couple of days I've gone to 37.5/30. Does that seem reasonable?

Feeling somewhat odd. Difficult to describe. Maybe woolly headed, bit dizzy, something like that.

Would 25/30 also be worth considering? Or is that a strange combo?

Should've got my RT3 tested when I had the thyroid profile done recently, so I could maybe get that done.

Also, am reducing steroids to nil (hopefully). Down to 1.5mg/day. No doubt that is making thyroid results fluctuate also.


Really not worth testing your rT3. It's expensive and doesn't help much. Do you have a copy of your labs - FT4/FT3 - before you started taking T3? That would tell you how well you were converting - at this point, it doesn't really matter if you were converting to rT3.

So, rather than spend the money on that, I would get my vit D, vit B12, folate and ferritin tested, to see if they're optimal.

There's no such thing as a strange combo. There's just the combo that suits you best. When you're hypo, there's really no point in aiming to mimic the ratios of a euthyroid person because we no-longer function the same way. You just need to find what makes you feel better. And even if that's T3 only, so be it. It you don't convert well, there's no point in insisting on having high levels of FT4. If I were you - and a lot of people would probably disagree with me - but if it were me, I would go back to the doses you were on before, and increase the T3.

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Thanks greygoose.

Vit D, ferritin, B12, folate etc. all OK.

I know I don't convert T4 very well, that was the reason I first went onto thyroid replacement.

I know I need a good dollop at least of T3, but found I felt a little more 'balanced', for want of a better word, when at least some T4 was added.

Longwinded, painful trial and error process to find the right combo for me. Made more so by unhelpful endos!

I'm now trying 50/30 to see what impact that has on symptoms and, if I stay on that level for a while, will retest in due course.


Yes, I know you know you don't convert T4 very well - I was just wondering how badly not very well was, if you see what I mean. If your FT4 had been right at the top of the range, and the FT3 had been right at the bottom, then just a tiny dose of T4 would probably do the trick, just to keep you balanced, as you say. But, you would certainly need much more T4 than T3. Which is why I say ratios for healthy people are helpful, because we aren't healthy.

Do you take selenium to help conversion? Have you had your cortisol tested?

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I don't take a selenium supplement but do eat brazils every day. Cortisol is OK at around 460 (can't remember what the units are). Daresay higher might be more 'optimal' but at least I do have some!

Did you mean ratios for healthy people AREN'T helpful???

The earliest thyroid results I can lay my hands on right now show TSH 1.4 [0.34-5.6]; FT4 11.1 [7.5-21.1]; FT3 5.0 [3.7-10.4]. I have no idea though if I was any meds at that time! I may have been taking a little Armour, which is what I was put on initially by an integrated practictioner. I wonder if I might not be better off on NDT and working with perhaps my naturopathic doctor on this. Might be easier to experiment and negotiate doses.

Meanwhile, 30mcg T3 for a few days has at least improved bowel function! Which convinces me I needed more. Will see how it goes.

Thank you for your very helpful input.


Yes, I did mean that ratios for healthy people aren't helpful. Sorry!

If you were on NDT at the time of that test, then you can't tell how you're converting. You need to be on T4 only to tell that. I just assumed you'd started on levo like the majority of people. So, you actually don't know if you're a bad converter if you started out on NDT, do you. Both your Frees were low in that test.

If 30 mcg T3 has increased your bowel movement, then that sounds like a good start. Try increasing T3 a little, and leaving the T4 where it is.


Well, I think I DID know that I was a bad converter BEFORE those test results or wouldn't have been put on thyroid replacement. L-o-n-g time ago, tho, and I have trouble remembering the last 5 minutes! Don't rate my chances of finding the very original results.

Yes, I'll see how I get on. Endo won't be pleased! Which will be a pain if I start having a tussle with the NHS to get the meds I want. Ho hum, one step at a time!

Thanks, Judy


Umm... no, that's not why people are put on thyroid hormone replacement. It's because they have a high TSH and low Frees - because they're hypo. Not all hypos are bad converters.


Fair point but it most definitely WAS the reason thyroid meds were advised in my case. I do remember that. My TSH has never been high. This wasn't an NHS decision, it was made by an integrated practitioner.


OK, in which case, it does not make any sense to me that you are taking such a high dose of T4. It's possible that the unconverted T4 is making you feel bad.

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Yes you could well be right.

This is proving very tricky.


Honestly, if it were me, I would start from T3 only, and gradually add in a little T4 to tolerance. You really don't want a lot of unconverted T4 hanging around.

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Again, I think you may well be right. Need to 'go back' a few steps and correct the balance.

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It all depends on whether you have any working thyroid left or not. If you have some thyroid left, then it will be making some T4 and T3 and your extra dose makes up for the rest. I notice your TSH on the second occasion was far smaller than the first. Thus your overall T4/T3 dose is sufficient to suppress the pituitary. However in such circumstances, extra T4 in your dose can be inhibitng T4-T3 conversion in your body, so that though your T3 dose is the same, the T3 produced by your body is reduced somewhat. Depending on your body's sensitivity to T4 this could be the explanation.


Thanks. Yes, I have been thinking of suppressed T4-T3 conversion from more T4. Possibly RT3 involved as said above.

I might experiment tomorrow with 25/30.


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