Thyroid UK
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Some T3 questions

Hi all,

I've got Hashi's and am on Levo since november 2014. I'm being treated by a endo which is going well since he thinks you should treat the symptoms and not the blood results. Unfortunately I've still not found the right dose for my body and I don't feel well. I just increased my dose to 100mcg Levo so maybe this will be better for me. Latest results on 87,5mcg are TSH 2,66 (range 0,35 - 4,70) and FT4 17 (range 9-19).

In April I have a blood test and appointment again with my endo. I'm getting frustrated that it takes so long and of course like I think we all have I'm afraid that it will never get better. I must tell you I read a lot about the thyroid so I know all the diet/vitamins/minerals advices and work on that since beginning the levo.

I'm thinking about asking my endo how he thinks about a trial of T3. I've got some questions I would like to get answered and Google isn't getting me the answers I'm looking for. My questions are;

- How long do your FT4 levels need to be 'perfect' and stable before thinking about adding T3?

- Does the T3 makes you feel normal/healthy/better or does it make you slightly hyper?

- How long do you need to take it (trial) to see if you can benefit of it (days/weeks/months)?

- Do you need to get your FT3 tested first and if so, what if the results are in the upper range but you still have symptoms, can you still benefit of T3?

Thank you for taking the time to read this and I hope I can get some more information.

11 Replies

I think the criteria should be 'how the patient feels' on any particular thyroid hormone. To answer your question:-

Does the T3 makes you feel normal/healthy/better

My answer is yes, yes, and yes. I have never been hyper and as I mentioned in another post earlier, I mistakenly took an extra day's dose of t3 (with a gap of about 12 hours) and expected some 'signs' but I had none at all and am now on my once daily dose of just under 50mcg of T3.

On levo I was permanently very unwell with more clinical symptoms than before diagnosis with TSH of 100.


The question isn't about how 'perfect' levels can be as they might vary from day to day. It is how a dose affect us, i.e. how do we feel, whether on levo alone, T4/T3, NDT or T3 only. It's a pity we cannot be allowed to trial various combinations on a trial basis but if we hit on the right one for us more or less straight away stay on that one.

Many people do fine on levothyroxine, it is just that those who don't search the internet and most of those on this forum levothyroxine hasn't done them much favours.


I agree to that. When did you started T3? Did you feel better right away or after a period of time? Also, was your FT3 tested before treatment?


Flower3, You were a little undermedicated to have TSH 2.66 but FT4 17 is very good. Most people will be well when TSH is just above or below 1.0 with FT4 in the upper range. The increase to 100mcg will bring down TSH and will raise FT4 to top of range.

You need to know what your FT3 result is to determine how well you are converting T4 to T3. NHS won't usually test FT3 unless TSH is suppressed <0.03 but you can order private thyroid tests from Blue Horizon or Genova via

If TSH is 1.0 or lower, FT4 high in range, and FT3 low in range, it indicates poor conversion and you will almost certainly benefit from adding T3 to T4. If FT3 is high in range you are unlikely to feel any benefit from adding T3 and may feel overmedicated. FT3 should remain within range.

Too much T3 or T4 can make you feel hyper, but some patients have levels over range which means they are overmedicated, without necessarily feeling hyper.

A 3 months trial is usually sufficient to tell whether adding T3 is beneficial. 10mcg T3 is equivalent to 30mcg T4. If FT4 is top of range it is T4 dose may be reduced by 25mcg for every 10mcg T3 added. If patients don't experience significant improvement the trial is usually discontinued and symptoms dismissed as non-thyroidal. Unfortunately some doctors reduce T4 too much when adding T3 so the patient doesn't feel any benefit.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

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Thanks so much, Clutter. Last time FT3 was checked (couple of months ago) it was okay.

Like you also say my FT4 looks good now, I increased 12,5mcg because of the TSH and the most important; because I feel unwell.

I know they say it can take some time to feel better once you have good levels but how long? It's difficult and I guess the only thing I can do is wait and discuss the T3 with my endo.


Flower3, what was the FT3 result and range? Okay is an opinion.

It usually takes 7-10 days to absorb the dose increase before symptoms start improving and then symptoms can lag behind good biochemistry by a couple of months.


I had to look it up, FT3 was tested 10 months ago when I was hyper;

TSH 0,01 (range 0,27 - 4,20)

FT4 20,1 (range 10 - 19)

FT3 5,6 (range 3,5 - 5,9)

Looks good, right? I mean I had to decrease then but FT3 seemed to react like you would expect with that FT4(?).

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Flower3, really all that tells you is that FT3 was good on whatever dose you were taking 10 months ago. It will have dropped when dose was reduced but the question is by how much?

If you don't feel better in a couple of months after this recent dose increase it may be worth having a private FT3 test to see.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thanks Clutter and you're right. I will wait and see and discuss this with my endo.


why do some patients on ndt have good ft3 on test and low ft4


I'm not a pro on this subject but if I've learned it correctly, taking T3 makes your TSH very low and FT4 as well.

Normally your body converts T4 into T3 so if you take T3 directly I don't think you need the T4 that much (which is why your body lowers it).

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