Total thyroxine — bound plus free.
What is it
Total T4 includes both protein-bound and free thyroxine. As with Total T3, it can be influenced by carrier protein changes.
Why it's measured
Total T4 has been used historically in thyroid evaluation, though Free T4 is now more commonly emphasized in published research.
Reference range
Standard laboratory reference
4.5 – 12.0 μg/dL
Reference ranges vary by laboratory. Your individual reference range will appear on your test report and should be interpreted by your physician in the context of your overall health profile.
What results may indicate
Elevated
Has been associated with hyperthyroidism in research literature.
Lower
Has been associated with hypothyroidism in research literature.
These associations are general. They are not a personal diagnosis or prediction. Discuss your individual results with your physician in the context of your full health profile.
When it's measured
Sometimes measured in comprehensive thyroid panels.
Related markers
Measured in
A complete look at your heart, hormones, metabolism, inflammation, and longevity systems — drawn at Quest or LabCorp, reviewed by a U.S.-licensed physician.
Explore the Apex Panel →This information is for general educational purposes only and is not medical advice. Lab results alone are not intended to diagnose, treat, or cure any condition and do not replace the advice of a healthcare provider. OPTML does not offer medical advice, a diagnosis, medical treatment, or any form of medical opinion.