Should I add more T3 after blood results? - Thyroid UK

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Should I add more T3 after blood results?


Hi, I don’t think GP gets the fact that taking T3 lowers T4 levels. However after latest blood results he has told me to increase T4:

TSH 0.03 (0.37-4.2)

T4 10 (12-22)

T3 4.2 (3.10-6.8)

I have been taking 75mcg T4 and 20mcg T3 .

GP is concerned that T4 is below range and told me to take 100 mcg to try and raise it.

From previous post some time ago I have used the calculator:

FT4 -20%

FT3 29.73%

Should I take more T3 to get it in the upper range? And if so how much?

Thank you in advance for any help or suggestions.

4 Replies


Something is wrong with the calculation. If your FT4 is 10 with a range of 12-22, it can't possibly be 20% through the range, it is below range so it will be in minus figures, it would be less than 0%.

Only you will know what balance of T4/T3 will suit you, it's a lot of trial and error. I take a combination of Levo and T3 (nothing to do with GP though), and I found, after many months of tweaking, that I am best when both my FT4 and FT3 are around 75% through range. When I lowered my Levo to a point where my FT4 was 12.8 (12-22) I couldn't function, and it took me quite a long time to increase back to where I felt reasonably well.

PS - I have deleted your duplicate post.

Hi SeasideSusie thank you for your reply.

The calculation is minus 20%, sorry it’s not clear in my post.

How did you get your FT4 up with taking T3?

Thank you for deleting the duplicate post.

in reply to Theminx


How did you get your FT4 up with taking T3?

I had been tweaking Levo and T3 doses for months until 100 Levo/25 T3 seemed about right, but my FT4 was 19.5 (12-22) and I thought maybe too high so I reduced my Levo from 100mcg to 75mcg which resulted in those devastating effects. I increased back to 100mcg, keeping my T3 the same dose. It has taken a year but now I seem to need 112.5 Levo with 25 T3 and I feel my thyroid is stable on those doses, last test FT4 was 72% through range and FT3 76%. But those figures wouldn't suit everyone, it is all so individual.

Thank you. Will try 100mcg Levo with a little more T3 and see how it goes

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