Hormone — Thyroid Axis
Free T4
Free T4 is the storage form of thyroid hormone, converted to T3 in tissues.
Reference range
Adult reference: ~0.8–1.8 ng/dL. Functional optimization context only — not a diagnostic assertion. Range varies by lab, age, and sex.
Why it matters
Free T4 is the thyroid axis's storage form. Its level, alongside TSH and free T3, completes a real thyroid workup. Reading all three reveals whether the issue is pituitary signaling, gland output, or peripheral conversion.
How REVRCEL clinicians read it
Always paired with TSH and free T3.
Included in
- Hormone Optimization Panel
Related biomarkers
Statements have not been evaluated by the FDA. This page is educational and is not medical advice.