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How To Calculate Your Level Of Reverse T3


Never feeling RIGHT on any dose of thyroid hormone replacement. One dose will be too low and another produce hyper symptoms with still hypo symptoms remaining. Adrenals that are miserably unresponsive to any dose of cortisol, fluid retention, normal temps to subnormal temps while still feeling hypo, Free T4 over mid range.



Answer: This confuses everyone! The problem is we want to know how much FT3 we have relative to the amount of rT3. To be in best health, we want at least twenty times as much T3 as RT3, so a ratio greater than 20.

But labs report both FT3 and RT3 in two different ways, so we often have to do some conversion to make sure we are comparing apples to apples.

Free T3 is sometimes reported as a number that is in the hundreds, like 332, and other times it is a number with only one digit before the decimal, like 3.3.

Similarly, reverse T3 is reported differently also. Sometimes it is a number that is in the hundreds, like 240, and other times it is a two digit number like 24.

If life were simple, all labs would report the FT3 in the hundreds and the rT3 as a two-digit number and we’d have no conversions to do at all, we’d just divide directly. The ratio would just be FT3/RT3 and we’d all understand it easily.

But we have to make adjustments when the labs don’t do it the way we like! So this is how to calculate the FT3 : RT3 ratio:

~take the FT3 result
~multiply it by 100 if it’s not in the hundreds
~multiply it by 10 if the rT3 is in the hundreds
~divide by the rT3 result

I know this formula sounds confusing, so let’s look at some examples. And if you don’t understand, just find the example with results similar to yours and do it that way!

Example #1

Free T3 476
RT3 24

The FT3 is in the hundreds and the RT3 is a two digit number, so this is the simplest example.

This ratio is 476 / 24 = 19.8 (under 20, this means you have an RT3 issue although a very slight one)

Example #2

FreeT3 3.89
RT3 12

The FT3 is not in the hundreds so we have to multiply by 100. This ratio is 3.89 * 100 / 12 = 32.4 (over 20, good)

Example #3

Free T3 389
RT3 312

The RT3 is in the hundreds so we have to multiply by 10. This ratio is 389 * 10 / 312 = 12.5 (well under 20, definite RT3 problem)

Example #4

Free T3 3.9
rT3 220

The FT3 is not in the hundreds, so we have to multiply by 100 AND the RT3 is in the hundreds so we have to multiply by 10, so we have to multiply by 1000 overall. This ratio is 3.9 x 1000 / 220 = 17.7 (under 20, not good)
If you have a RT3 problem, consider joining the yahoo group at:

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