Thyroid UK
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RT3/FT3 Ratio


I just used STTM to calculate my reverse T3 Ratio.

My RT3 is (0.62 ug/L) and the normal range is (0.09-0.35)

My FT3 is (3.99 pmo/L), and the normal range is (3.1-6.8)

And the ratio I got from STTM is: (4.2). can you please tell me how bad is this ratio as I feel very sick, and I know that might be due to the high amount of Reverse T3, which has reduced my T3 absorption.


6 Replies

This is a link by one of our Adviser (deceased) and about Reverse T3.

If you go to the date March 24, 1999 to read.


RT3 will not make you feel sick, and will not reduce your T3 absorption. You are sick because your dose is too low and therefore your FT3 is too low. What are you taking, and how much? Do you have a result for the FT4?


You are right that I'm currently under medicated as just had blood test today and my TSH is elivated

The blood test from today is as follows:

Anti ThyroPeroxidase Abs (TPO)113.97 (< 5.61


Free T3 (Triiodothyronine)5.15 (3.1 - 6.8


Free T4 (Thyroxine)19.54 (12 - 22


TSH3.170 (0.27 - 4.2


Vitamin D (25-OH-Cholecalciferol)63.9 (50 - 150)



You're welcome. :)


If you are worried about your ratio and have to work it out yourself rather than have it done by a lab when testing FT3 and rT3 at the same time, then you have to make sure that the unit of measurement is the same for both FT3 and rT3 (it tells you that on the SSTM website).

As your rT3 is in ug/L and your FT3 is in pmol/L did you use those figures or did you change one of them so that the units of measurement were the same? If not then your ratio is incorrect.


I used the figures as is. STTM gives the option to scroll down and choose the unit of measurement. I put my T3 in pmol/L and put my RT3 in ug/L.

Does it work that way?


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