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Thyroid UK
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Switching From Compounded T4/T3 Back to T4 Only

Hi All–

I gave it a shot. I was on compounded T4/T3 for almost three months (T4=30mcgs, T3=70mcgs). Though my RT3 did come down, I ended up being more tired and gained more weight – 10 additional unwanted pounds in three months. I was told I would lose, I guess I'm one of the unlucky few that doesn't respond to T3 that way.

So I'm going to switch back from this dose to 125mcgs Synthroid and attack my adrenals, vitamin issues, and diet. Hoping that will help my T4 to T3 conversion and keep RT3 down.

My question is – can I just switch right back to my previous T4 dose? I want to do this safely, but also get on with it. Should I stop everything for a few days then re-introduce T4?

Any and all thoughts are greatly appreciated. Thanks!


5 Replies


Have you transposed the T4 and T3 doses?

30mcg T4 + 70mcg T3 = 240mcg Synthroid.

70mcg T4 + 30mcg T3 = 160mcg Synthroid.

Either way, you are likely to be undermedicated on 125mcg Synthroid.

You can switch straight over. No need to skip doses.


Thanks for the response Clutter. I didn’t transpose the numbers — that’s what my doctor prescribed, despite my reservations. Odd thing is, I didn’t even feel like I was taking a high dose. My numbers ended up looking good, but I gained weight and have been tired all the time.

I will switch directly over. Will my body take a long time to begin converting again?



If you were overmedicated on 30mcg T4 + 70mcg T3 that could be why you gained weight. thyroid.about.com/od/thyroi... If you weren't overmedicated then you're going to be undermedicated on 125mcg.

If you weren't converting well before on Levothyroxine you probably won't when you switch back.


Interesting. My labs didn't indicate that I was overmedicated. My FT3 was right at the top of the range, FT4 was lower in the range, and RT3 was down to 8 (from 32). Oddly my TSH was still a 2. I thought it would be suppressed. Again, I never felt more energy or any kind of bump in metabolism, even with 70mcgs T3! I just don't think my body was using it at all, and maybe it doesn't like all that T3 pooling?

Regardless, the weight gain must be from the change in meds, so I'm forced to consider switching things up again. I really hope that working on my vitamin deficiencies, diet, and adding back adrenal support will help me convert like I used to on T4 only. I had many great years on it.

I suppose another option is changing up the ratio, but honestly, I wouldn't know what to do there.

Thanks for the responses. It's much appreciated.


You know maybe you do need to look at your vits and minerals and optimise those as well. Would it not be worth sticking with it to see if tdoing that makes a difference rather than switching completely back? The uptake of thyroid hormones into the actual cells is an area so little is known about and cannot be measured.....if only....


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