Total T4
Total T4 measures both protein-bound and free thyroxine in blood. Because more than 99 percent is bound to thyroid binding globulin, albumin, and transthyretin, total T4 is influenced by changes in binding proteins caused by pregnancy, estrogen, or liver disease. Free T4 is preferred in most clinical settings for assessing thyroid status.
4 providers include this
Thyroid Function
4.5-12.0 μg/dL
What is Total T4?
Total T4 measures both protein-bound and free thyroxine in blood. Because more than 99 percent is bound to thyroid binding globulin, albumin, and transthyretin, total T4 is influenced by changes in binding proteins caused by pregnancy, estrogen, or liver disease. Free T4 is preferred in most clinical settings for assessing thyroid status.
Why It Matters
Measures bound and free T4. Less useful than free T4 since affected by binding proteins. Can be misleading in pregnancy or estrogen use.
Which Providers Test Total T4?
Full Provider Comparison
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | — | $349 | 65 |
 Labcorp OnDemand | — | $398 | 40+ |
| — | $486 | 40+ | |
| — | $449 | 288 | |
| ✓ | $349 | 100+ | |
| — | $829 | 54 | |
 Function Health | — | $365 | 160+ |
| — | $250 | 65 | |
| — | $495 | 80+ | |
| — | $895 | 100+ | |
| — | $1950 | 130+ | |
| ✓ | $375 | 95+ | |
| — | $Varies | 75+ | |
| — | $190 | 100+ | |
| — | $99 | 50 | |
| — | $124 | 60 | |
| — | $349 | 130+ | |
| — | $349 | 80+ | |
| — | $375 | 85 | |
| ✓ | $700 | 128 | |
| — | $99 | 100+ |
Frequently Asked Questions
What is Total T4?
Total T4 measures both protein-bound and free thyroxine in blood. Because more than 99 percent is bound to thyroid binding globulin, albumin, and transthyretin, total T4 is influenced by changes in binding proteins caused by pregnancy, estrogen, or liver disease. Free T4 is preferred in most clinical settings for assessing thyroid status.
What is the optimal range for Total T4?
The standard reference range for Total T4 is 4.5-12.0 μg/dL. Optimal ranges may differ based on individual health goals and expert recommendations.
Which blood test providers include Total T4?
4 out of 22 blood testing providers include Total T4 in their panels. This biomarker has limited availability.
What category does Total T4 fall under?
Total T4 is categorized under Thyroid Function. This category includes biomarkers that help assess related aspects of health and wellness.
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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.
Last reviewed:2026-04-12