Triiodothyronine/Triiodothyronine.reverse

ChemistryAlso known as: T3/T3Reverse SerPl-RtoN/A

Measures the ratio of active T3 to reverse T3 thyroid hormones in your blood.

Normal Range
Consult your provider
N/A
Abnormal Levels
Consult your provider
Specimen Type
Blood

Why This Biomarker Matters

This ratio reflects thyroid hormone conversion efficiency. An unfavorable ratio indicates impaired metabolism and may explain fatigue, weight gain, or cold sensitivity despite normal TSH.

Overview

This test measures the ratio of active thyroid hormone (T3) to reverse T3 (rT3), reflecting thyroid hormone metabolism efficiency. T3 is the active form that powers metabolism, while reverse T3 is inactive and can block T3 action. An unfavorable ratio (high rT3 relative to T3) suggests poor conversion, seen in stress, illness, or metabolic dysfunction. This ratio helps assess thyroid function beyond standard TSH testing and guides treatment decisions.

Technical Information (LOINC Codes)

Standardized laboratory codes for this biomarker

57899-7Primary
Triiodothyronine (T3)/Triiodothyronine (T3).reverse [Ratio] in Serum or Plasma

Available Lab Tests

Order tests that measure this biomarker

Reverse T3

$30.64
Results in 3-5 business days

T3 Free Tracer Dialysis

$268.40

Total T3

$18.76
Results in 1-2 business days
Triiodothyronine/Triiodothyronine.reverse: Normal Range, Testing & Clinical Significance | Healos | Healos