Free Thyroxine Index

FTI is a calculated score that estimates the amount of free, active T4 in your body based on Total T4 and T3 Uptake. It helps correct for abnormal levels of thyroid-binding proteins, giving you a better idea of how much hormone is actually usable. It’s especially useful when SHBG or TBG is skewed due to stress, estrogen, or liver issues—and gives you another way to assess thyroid status beyond TSH alone.

Unit

%

Health impacts

Energy · Thyroid