LabwiseFree Thyroxine Index
The free thyroxine index is calculated from total T4 and T3 uptake as an older estimate of free thyroid hormone.
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What Free Thyroxine Index measures
The free thyroxine index is calculated from total T4 and T3 uptake as an older estimate of free thyroid hormone.
If your Free Thyroxine Index is low
A lower index is commonly associated with an underactive thyroid.
Commonly associated with
- Underactive thyroid
If your Free Thyroxine Index is high
A higher index is commonly associated with an overactive thyroid.
Commonly associated with
- Overactive thyroid
Typical reference range
| Group | Typical range |
|---|---|
| Adults | 1.2 – 4.9 |
Typical adult values used by many US labs. Your own report prints the range your lab validated for its method, and that range is the one that counts. Labwise always uses the printed range first.
If it is within range
Your free thyroxine index is within the range printed by your lab.
Also listed as
FTI, T7
Related tests
This page is general information about what a laboratory test measures and what results outside a reference range are commonly associated with. It is not medical advice, does not diagnose any condition and does not replace your clinician. Discuss your results with your healthcare provider.