Hormone — Thyroid Axis
Free T3
Free T3 is the active thyroid hormone available to tissues.
Reference range
Adult reference: ~2.3–4.2 pg/mL. Functional optimization context only — not a diagnostic assertion. Range varies by lab, age, and sex.
Why it matters
Free T3 is the biologically active thyroid hormone. Its level — relative to free T4 and TSH — determines how the thyroid axis is actually performing at the tissue level. Optimization-minded clinicians read all three rather than relying on TSH alone.
How REVRCEL clinicians read it
Always paired with TSH and free T4 for a complete thyroid read.
Included in
- Hormone Optimization Panel
Common questions
Why test free T3?
It is the active thyroid hormone. TSH and free T4 alone can miss cases where free T3 is low.
Related biomarkers
Statements have not been evaluated by the FDA. This page is educational and is not medical advice.