rT3
An inactive form of T3 — can be elevated during illness or stress.
What is it
Reverse T3 is an isomer of T3 that does not activate thyroid receptors. Its production rises during severe illness, caloric restriction, and certain stress states.
Why it's measured
Reverse T3 has been studied in research on non-thyroidal illness syndrome and the body's response to physiologic stress.
Reference range
Standard laboratory reference
9 – 24 ng/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 severe illness, caloric restriction, and stress states in research literature.
Lower
Is generally not clinically concerning in isolation.
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
Used in specialized thyroid evaluation, particularly when symptoms persist despite normal standard thyroid markers.
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.