rT3 in Serum

Reverse total T3 is an inactive metabolite of T4. It is useful for differentiating euthyroid sick syndrome from central hypothyroidism.

Also known as:

Reverse Triiodothyronine (Total)

S-rT3

Reverse T3

rT3 ranges

Interpret your result

"Normal" lab range for rT3 is between 8 and 25 ng/dL:

According to Peter Attia, rT3 should be below 12 ng/dL:

According to OptimalDX, rT3 should be between 10 and 25 ng/dL:

According to Rupa Health, rT3 should be below 15 ng/dL:

Optimal range

Optimal range for rT3 appears to be between 10 and 20 ng/dL:

Why this optimal range?

This range applies to the LC/MS-MS method, since there is huge variability between methods. The available research is limited, and reported cutoffs across sources are highly inconsistent, so the proposed optimal range should not be considered definitive.

Despite common belief and one old, frequently cited study, the American Thyroid Association concludes that reverse T3 "does not bind or compete with T3 at the T3 receptor". Therefore, it is not an antagonist.

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