Thyroid UK

More fatigue with T3!


Male, 39 years old, 71.5 kg.

Just want to know if someone here have a similar experience (more fatigue) whit T3.

I tried to ad T3 to my 100 mcg T4 dose but cannot tolerate it. Tried 2,5 mcg, 5 mcg and 10 mcg and the results are all the same: I fell more fatigued with it, and irritable to.

It is an indication that I am not ready for T3 or that my body don’t need it?

Whit 100 mcg of synthroid, my TSH is 0,19 uUI/ml, my Free T4 is at 65,45% of the reference range (1,42 ng/dl Ref: 0,70 – 1,80 ng/dl), and free T3 is at 65 % of the reference range (0,33 ng/dl Ref: 0,20 – 0,40).

Is this an indication that I am a good converter? I never had low freeT3 in any blood test, even without syntroid my FreeT3 is at 70% of the reference range, the problem is that whit no medication my TSH goes to 5 and free T4 drops to low on range.

Whit T4 only, my face is a little less puffy, I have more energy and feel more calm and relaxed, and I don’t have more cold hands and feet, but interesting, my wake up temperature is still low (35.9 Celsius) and peaks to 36.6 Celsius at 6 pm, but I can reach the desired 37 Celsius.

I tried T3 to see If the pain on the joints of my legs gets better, whit no results. Maybe the heaviness on my legs comes from a magnesium deficiency??

I think is now time to increase to 125 mcg or maybe 112 mcg, since in my country 112 mcg is available.

Thank you.

8 Replies


You appear to be converting well enough on 100mcg and it doesn't look like you need additional T3. It might be worth trying 112mcg to see whether symptoms improve in a few weeks.

Hypothyroid patients often have low ferritin, vitamin D, B12 and folate which can cause fatigue similar to hypothyroid symptoms. It may be worth asking your GP to test.


I don't bother too much about blood tests and concentrate on how I am feeling with a particular thyroid hormone or dose. That's because I do know I am hypothyroid. Sometimes our pulse or temp may not come back to what was normal for us, if we knew what it was in the first place. In the past patients were prescribed NDT due to their clinical symptoms alone and it was increased until patient felt well. Adjusting doses up/down accordingly.

Maybe this will be helpful:-

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I become tired if I am overmedicated in the same way as if I was hypo and other symptoms are often the same either way. You may have needed to reduce your T4 to add T3 rather than just adding it on top especially with tsh of 0.19 on your original 100T4. So if you still wanted to try it, maybe try with a slight reduction of T4?

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I tried whit a reduction of the T4 too and the same effect, more fatigue (tried whit 75 mcg T4). So, it looks that the problem is the T3.


Okay, yes my friend can't tolerate T3 either so maybe just doesn't suit you?


Did some reading and found that for each 1mcg of T3 added we must reduce T4 by 4 mcg. Ok, but also, if the FreeT4 is high and TSH is already suppressed on T4 only, we must reduce the T4 dose at least for one week before adding T3. And this I didn’t did.

Will experiment this.

The way it is done in my body, whit 112 mcg of T4, my FreeT4 will go up and my FreeT3 to, and I have read that the magical range for freeT3 is at the top quarter of the reference range, so at least 75% of the range. Whit this in mind, I have a question:

Any problem in having FreeT4 very high (say, at 85-100% in the reference range) to have FreeT3 at the 75% range?

I am trying to understand this.

Thank you.


The idea that 4 micrograms of levothyroxine is equivalent to 1 microgram of triiodothyronine (T3/Liothyronine) is difficult.

In one person, that might have some truth, but there really isn't a nice, neat number that expresses what happens. Even if that worked to begin with, after a while on liothyronine, things change and so would the number.

What happens, happens. You can use a formula to make a guess - but that really is all it will be. A better guess than rolling dice, to be sure, but not an accurate prediction.


The pains and heaviness in my legs only cleared up once I went gluten free so may be worth looking at diet. Also, you may be deficient elsewhere :-)

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