Free T3 (Free Triiodothyronine)
Here’s what it reflects — and what to do about it.
Longetic pulls together every lab and record you’ve had, follows how Free T3 (Free Triiodothyronine) changes over time, and explains what’s shifting — so you walk into your next appointment prepared, with reminders for retests along the way.
What is Free T3 (Free Triiodothyronine)?
The active, unbound portion of the thyroid hormone T3 that is free to enter your tissues.
T3 (triiodothyronine) is one of the two hormones your thyroid makes, and free T3 is the active portion not bound to proteins. It is used most often to help confirm and understand an overactive thyroid, interpreted together with TSH and free T4 rather than alone. Higher free T3 can be associated with hyperthyroidism. Note that free T3 assays are often less reliable than a total T3 measure, so free T3 is used selectively and total T3 is frequently preferred; a result only becomes meaningful alongside the rest of your thyroid values.
What to know about Free T3 (Free Triiodothyronine)
Understanding Free T3 (Free Triiodothyronine) means knowing what it reflects, what tends to move it, and the signs that suggest it’s worth a closer look — so you can bring the right questions to your next appointment.
This glossary entry is for informational purposes only and is not a substitute for professional medical advice. Read our Medical Disclaimer.
References
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