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Thyroid UK
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When is T3 more beneficial?

Hi everyone, my question is in the title. Do you have to have low blood T3 in order to benefit from adding medication?

I don't have low T3 but my TSH is completely suppressed, that is, most of the sample results came back with a TSH below 0.1 even prior to starting T4 medication. Not sure if T3 will help or not, I may try T3 but will need to import it at an expensive price.

5 Replies


If your TSH was <0.1 and FT4 was low when you were diagnosed it indicates secondary hypothyroidism instead of primary hypothyroidism which presents with high TSH.

If your FT3 is good there's no point in taking Liothyronine (T3) unless you are unable to tolerate Levothyroxine.

T3 won't raise TSH if that's what you are thinking. Adding T3 to Levothyroxine will make TSH lower.


No, not thinking to rise TSH, TSH can increase to normal range 1-1.5 only when my T4 gets very low in normal range. It is a confusing case as told by several doctors.

What I’m trying to achieve is to get better treatment than T4 only medication as my symptoms not fully healed even by increasing the dose so that T4 is in the upper quarter of normal range.

I see your point that T3 in normal range already and in fact is increasing as I attempted to increase T4.

So , the question then if T3 is not the answer and I already tried NDT, what else should I try and hope to make me feel better? Increasing TSH😅?



Where in range your FT4 and FT3 are matters. Can you post the results and ranges?

What dose Levothyroxine are you taking and what dose NDT were you taking? Some people have to try several brands of NDT to find one which suits them.


FT4 is 18.7 (10–28)

TSH 0.017 (.46-4.68)

My endo does not want to do FT3 anymore but from history, it always moves with FT4. I tried to increase my FT4 up to 25 and symptoms didn’t change.

For NDT trial, I took naturthroid.



TSH is low but not suppressed and FT4 is just shy of halfway through range.

I'm not clear what you were taking when you had the above results but I think there was scope to increase dose to raise TSH which would also raise FT3.

If you are taking NDT you do need FT3 tested to ensure FT3 remains within range and as a guide to adequate dosing.


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