Confused by Medichecks reverse T3 ratio calcula... - Thyroid UK

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Confused by Medichecks reverse T3 ratio calculation


As the NHS will not do the rT3 test and my endo suggested it should be done, I have these recent Medichecks results. The reverse T3 value alone is low, which is good I think as I have been supplementing with iron, selenium and supporting my liver & adrenals for over a year now. However I am confused as to how Medichecks have calculated the rT3 ratio and come up with the figure 26.57. Which according to Dr Kent Holtorf is showing healthy amounts of RT3, using the FT3/RT3 ratio as the ratio result should be 20 or larger.

In STTM book 2nd edition p175 it says:

"3) If the RT3 is ng/dL and Free T3 is pg/dL (or pmol/L), divide the Free T3 by the RT3" 4.49/11= 0.41 not 26.57 value by Medichecks

Using the STTM beta calculator it is even more confusing with point number "4) IF pg/mL on top and ug/L on bottom, and one is a decimal and the other a whole number...won’t work"

Please can someone hold my hand and walk me through this 0.41 correct or 26.57 correct and if the latter how did Medichecks calculate it.

Just to say my endo has been fiddling with my combination therapy dose for over a year and these test results are for a TEVA LT4 75mcg/Mercury LT3 25mcg {BID 15mcg/10mcg}. I continue to have symptoms of exhaustion and poor cognition. The GP and Endo are upperty about the suppressed TSH so the LT4 has now been reduced to 50mcg ***eye rolling with long sigh moment***

Please see my profile for further information :-)

Thank you lovely people!

11 Replies

I do wish people would get a grip and quote values in the same kind of units. The intransigence of the US in refusing to use SI units confuses everyone. From your data, I think the rT3 is 169 pmol/L and dividing that by 4.49 gives 37.6. I certainly don't get Medichecks value but I suspect this is another illegitimate way of mixing up apples and pears. Anyway, however calculated, the ratio is within the reference range.

amasufindme in reply to diogenes

Thank you have confused me further :-) (lol)... RT3 169pmol/L from 11ng/dL...I have now found this useful converter I understand where you get that value 169 now. It is the STTM book that is confusing me...

I'm very interested to know what your endo is going to do with that information on your rT3/rT3 ratio. :)

I don't know what he will do...I am seeing him in 3 weeks and my expectations have been reduced to a new low level... I suppose if it is in range then its something else to tick off and he can back to fiddling with my dose :-)

I doubt it would have been rT3 causing problems, anyway.

You can refuse to let him fiddle with your dose, you know. He's not all-powerful!


If you convert the RT3 to pmol/L units this gives 169 (rounded) as diogenes says. If you then use the STTM calculator using 4.49 pmol/L and 169 pmol/L, that gives you Medichecks' ratio of 26.6 (rounded).

"If the RT3 is ng/dL and Free T3 is pg/dL (or pmol/L), divide the Free T3 by the RT3"

This is nonsense. pg/dL is completely different to pmol/L. Not just different units but they are not equivalent. In any event the ratio is meaningless. fT3 levels vary and serum fT3 does not reflect local levels of T3 produced by type-2 deiodinase. This ratio is pseudo science, I'd be wary of anyone who suggests it's use. Ask them to reference clinical studies that have deomstrated the validity of this ratio.

Use the STTM calculator. Plug in 4.49 on top, then convert to ug/l (divide ng/dL by 100) so .11 at the bottom. 4.49/.11 = 26.5

As it’s been said before me, unfortunately what’s seen in the pituitary doesn’t mean much when it comes to peripheral hypothyroidism. Still rather useful imo, although here I’m seeing low T4 and fT4 so I’d consider testing for TBG and raising it up.

Read up on peripheral hypothyroidism there:

Not sure whether my previous comment worked. Use STTM calculator. 4.49 divided by .11 (ug/l) = 26.5.

Read this - ratio above may not mean much when it comes to what happens out of the pituitary

Low t4 and fT4 and that TSH - I’d guess TBG is too low. I’d seriously reconsider the t4 drugs...

amasufindme in reply to Benaoao

Thanks Benaoao :-)

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