← Blood tests
Free T3 / Reverse T3 Ratio
Specialistalso —
What it isA ratio that captures the balance between active T3 production and inactive rT3 diversion in peripheral tissues.
DoesIndexes functional thyroid status at the tissue level — what's actually getting through to receptors.
GoodA high ratio signals strong active thyroid hormone availability and a metabolism running smoothly.
BadA low ratio indicates impaired conversion and tracks fatigue, weight gain, cognitive sluggishness, and chronic stress states.
- Standard
- No standard cutoff.
- Optimal
- 0.25–0.40 (higher is good)
- Modifiers
- Same as Free T3 and reverse T3.
How to optimize
- Lifestyle
- Adequate calories, sleep, stress management; avoid overtraining.
- Diet
- Adequate calories and carbs; iron, selenium, zinc.
- Supplements
- Selenium (200µg/day), zinc (15–30mg/day), iron if deficient.
- Peptides
- —
- Drugs
- Liothyronine in selected patients.
SeleniumZincIron
Reference ranges are general adult lab norms; optimal ranges are editorial picks from the longevity literature — not medical advice. Always interpret results with your physician.
within Thyroid