Thyroid UK

Lab confusion

I have been having trouble getting my levels optimal. I am currently on 2.5 grains of NP. Listed below are my most recent labs. I am unsure about the t3 to rt3 ratio. If I calculated it correctly it is 0.2 and I have no clue what is optimal. Help would be greatly appreciated.

Thyroxine (T4) Free, Direct, S

Reference RangeUnits 0.82-1.77ng/dL T4,Free(Direct)1.16

Triiodothyronine (T3)

Reference RangeUnits 71-180ng/dL

Triiodothyronine (T3)148


Reference RangeUnits 2.0-4.4pg/mL



Reference RangeUnits 0.450-4.500



Reference RangeUnits 4.5-12.0ug/dL Thyroxine (T4)6.9

Reverse T3, Serum

TestLowNormalHighReference RangeUnits 9.2-24.1ng/dL

Reverse T3, Serum18.4

1 Reply

1) The RT3 result by itself is moving above 11 (with a range that starts at 8 or 9) . We have seen that correspond with rising RT3.

2) The ratio between the Free T3/RT3 or the Total T3/RT3. i.e dividing the Free T3 by the Reverse T3 (Free T3 ÷ RT3) or dividing the Total T3 by the RT3 (total T3 ÷ RT3)…though they need to be in the same measurement or changed to the same measurement.

Using the FT3/RT3 ratio, and for healthy amounts of RT3, the ratio result should be 20 or larger according to Dr. Kent Holtorf (info below). If lower, you may have a problem. Janie has noted that many patients without an excess RT3 issue have a result of 23 or 24 or higher.

For the Total T3 ratio, it should be 10 or higher. The Institute of Functional Medicine supports the Total T3/RT3 ratio.

Figuring out your ratio is here.

What about Australian ranges? Other ranges that don’t begin with 8 or 9?

Australia RT3 ranges tend to be (140-540) or (170-450) pmol/L. With the former range, a healthy RT3 result would be around 165 or less. For the latter range, a healthy RT3 result would be around 196 or less.

The measurements have to be in the same equivalents. Either pg/ml or ug/dl or ng/dl

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