Free Thyroxine Index (FTI)

The Free Thyroxine Index (FTI) is a calculated value derived from total T4 and T3 uptake, used to estimate the amount of free (unbound) thyroxine in the blood.

Category: Thyroid Panel

Also known as: free thyroxine index

Reference range: 1.2–4.9 index (Source: ABIM)

Standard unit: index

High values may indicate

High FTI may suggest hyperthyroidism.

Low values may indicate

Low FTI may suggest hypothyroidism.

Source: BloodId admin-reviewed

Track your Free Thyroxine Index (FTI) over time with BloodId