Free Thyroxine Index (FTI)

Calculated estimate of free T4 using T3 uptake

1/22Providers
Thyroid FunctionCategory
1.4-3.8Reference

Limited Availability

1 providers include this

Category

Thyroid Function

Reference Range

1.4-3.8

What is Free Thyroxine Index (FTI)?

Calculated estimate of free T4 using T3 uptake

Why It Matters

Adjusts Total T4 for binding protein variations. Useful when binding proteins are abnormal (pregnancy, estrogen use). Correlates with metabolic status.

Reference Range: 1.4-3.8

Which Providers Test Free Thyroxine Index (FTI)?

Vitality Elite
Included in panel

Full Provider Comparison

ProviderIncludesAnnual CostBiomarkers
Superpower—$199100+ (150 with ratios)
WHOOP Advanced Labs—$34965
Labcorp OnDemand—$39830+
Life Extension—$48640+
Everlywell—$46883
Mito Health—$349100+
InsideTracker—$68048
Function Health—$499100+
Marek Health Base—$25045+
Marek Health Comprehensive—$49570+
Marek Health Complete—$895100+
Marek Health Executive—$1950150+
Blueprint Advanced—$1150110
Quest Health—$Varies75+
Empirical Health—$19085+
Oura Health Panels—$9950
SiPhox Health—$12560
Hims Labs Base—$19950
Hims Labs Advanced—$499120+
Healthspan—$34980+
Vitality Blueprint Standard—$37585
Vitality Blueprint Elite✓$700129

Ready to Test Free Thyroxine Index (FTI)?

1 providers include this biomarker in their panels

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Frequently Asked Questions

What does Free Thyroxine Index (FTI) test for?
Free Thyroxine Index (FTI) is a thyroid function biomarker. Calculated estimate of free T4 using T3 uptake The normal reference range is 1.4-3.8.
Which providers include Free Thyroxine Index (FTI)?
1 of 22 providers include this test:Vitality Elite.
How often should I test Free Thyroxine Index (FTI)?
For most people, testing 2-4 times per year is recommended to establish baseline levels and track trends. Consult your healthcare provider for personalized recommendations.
What is the optimal range?
The standard reference range is 1.4-3.8. Many functional medicine practitioners recommend tighter optimal ranges for peak health. Your ideal range may vary based on age, sex, and health goals.
Why is Free Thyroxine Index (FTI) important?
Adjusts Total T4 for binding protein variations. Useful when binding proteins are abnormal (pregnancy, estrogen use). Correlates with metabolic status.

Medical Disclaimer

This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.