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Free T3
Biologically active thyroid hormone
Also known as: FT3,Triiodothyronine Free,T3 Uptake
Reference Ranges
Clinical Reference
2.3 – 4.2 pg/mL
Optimal Range
3.0 – 4.0 pg/mL
Active thyroid hormone
Related Conditions
Hyperthyroidism
High
Hypothyroidism
Low
Food & Lifestyle Recommendations
🍎 Food
Ensure selenium (2-3 Brazil nuts/day) and zinc for T4→T3 conversion
Deiodinase enzymes require selenium as cofactor
Evidence-Backed Supplements
When Low
-
Required for T4→T3 conversion via deiodinases
Selenomethionine 100–200 mcg/day Morning -
Cofactor for T4→T3 conversion
Zinc picolinate or bisglycinate 15–30 mg/day Evening, away from iron/calcium
Questions to Ask Your Doctor
- Could my low T3 indicate a conversion problem from T4 rather than a primary thyroid issue? Selenium and zinc are cofactors for T4→T3 conversion
Upload your blood test to see how your Free T3 compares to reference and optimal ranges.
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