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01Markers · Thyroid

Free T3

Free triiodothyronine

T3 is the active form of thyroid hormone. The free T3 test measures the small share not bound to carrier proteins.

Measured in
Blood (serum)
Units
pg/mL, pmol/L
Also called
FT3, T3
  1. Ashwagandha
  2. Iron
  3. Berberine
  4. Collagen
  5. Creatine
  6. Finnish sauna
  7. HIIT
  8. L-carnitine
  9. L-theanine
  10. Lion's mane
  11. Magnesium
  12. Melatonin
  13. Milk thistle
  14. NAC
  15. NAD+
  16. Omega-3
  17. PQQ
  18. Red yeast rice
  19. Resveratrol
  20. Taurine
  21. Ubiquinol (CoQ10)
  22. Vitamin C
  23. Vitamin D3
  24. Vitamin E
  25. Vitamin K2
  26. Zinc
  27. Zone 2 cardio
Free T3 across the 27 supplements and practices researched so far · best evidence first

AWhat moves Free T3

2 of 27 studied

In human studies, 2 of the 27 supplements and practices researched so far raised free T3. 25 were never studied for it.
  • Supported 2
  • No effect 0
  • Conflicting 0
  • Not studied 25
See Free T3 on the evidence map →Check claims about Free T3 →

Moves it2

Human studies found a change. The grade reflects the studies behind it, from A (strongest) to D.

AshwagandhaRaisesGrade C

Ashwagandha raises free T3.

Lab or animal studies · 1 study linked

Studied in: Subclinical hypothyroid patients, Data limited in euthyroid

Open the Ashwagandha page →Check a claim about this →
IronRaisesGrade C

Iron raises free T3.

Small effect · 0 studies linked

This result is graded, but no study is linked to it yet. Treat it as unconfirmed.

Studied in: Iron deficient

T3 synthesis requires iron-dependent thyroid peroxidase. Iron repletion may modestly increase T3. Very thin evidence base (1 study in corpus).

Open the Iron page →Check a claim about this →

Not studied25

No usable human study has measured Free T3 with these. A gap is not a negative result: nobody has looked.

BerberineCollagenCreatineFinnish saunaHIITL-carnitineL-theanineLion's maneMagnesiumMelatoninMilk thistleNACNAD+Omega-3PQQRed yeast riceResveratrolTaurineUbiquinol (CoQ10)Vitamin CVitamin D3Vitamin EVitamin K2ZincZone 2 cardio

Commission research on a gap →

Why trials measure it. Trials of iodine, selenium and other compounds report it to see effects on thyroid hormone activity.

About this marker: Triiodothyronine (T3) Tests (MedlinePlus, U.S. National Library of Medicine).

Evidence states come from published human studies found in PubMed and OpenAlex and read by a model pipeline. "Not studied" means no usable human study was found for this marker, which is a gap, not a negative result. Every result links its studies so you can check it.

Research summary for education. Not medical advice.