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
Common questions
Total T4 includes both protein-bound and free thyroxine. As with Total T3, it can be influenced by carrier protein changes.
It's one of the markers used to build a fuller picture of your health. On its own it tells you very little, so it's most informative when reviewed alongside related markers.
It's measured from a standard blood draw at Quest or LabCorp. Total T4 is one of the markers included in the OPTML Apex Panel, where your results are read across systems and reviewed by a U.S.-licensed physician.
Reference ranges vary by laboratory, and a single value rarely tells the whole story. Review your result with a physician in the context of your other markers, symptoms, and history.
Total T4 is one signal among many. Answer a few quick questions and we’ll point you to the panel that fits.
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.