What does the Free Triiodothyronine test measure?

Why is Free Triiodothyronine measured?

Assesses T4-to-T3 conversion adequacy. Essential for patients on levothyroxine who remain symptomatic with normal TSH and Free T4.

Reference ranges

Standard reference

2.3–4.2 pg/mL (3.5–6.5 pmol/L)

Functional medicine optimal

3.0–4.0 pg/mL

Units

pg/mL, pmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.