ThyroidReported in ng/mLTotal triiodothyronine (Total T3)
The total amount of T3 in the blood, bound and unbound. T3 is the more active thyroid hormone.
What it measures
The thyroid releases mostly T4, and the body converts a share of it to T3. Total T3 measures both the T3 stuck to proteins and the small free fraction. It is reported here in nanograms per milliliter. Illness, pregnancy, and estrogen therapy change binding proteins, which can move a total level even when the free hormone has not changed much.
Why it is on the panel
T3 helps confirm an overactive pattern when TSH is low, and it adds context when someone has symptoms that TSH and T4 do not fully explain. It is not, by itself, a screening test for an underactive thyroid.
How to read it
Read total T3 with TSH and free T4. In typical hyperthyroidism, TSH is low and T3, T4, or both are high. A high total T3 with a normal free T4 can be an early overactive pattern. A low T3 during a serious illness is often “euthyroid sick” physiology, not a thyroid that needs hormone replacement.
When it runs higher
An overactive thyroid, thyroid inflammation releasing stored hormone, and extra binding protein can raise total T3. Symptoms that sometimes travel with a truly high free hormone include a fast heart rate, heat intolerance, tremor, and weight loss.
When it runs lower
Severe illness, some medicines, and low binding proteins can lower total T3. An underactive thyroid more reliably shows up as a high TSH, with free T4 falling later. A lone mildly low total T3 is easy to over-call.
Same group
Other Thyroid tests
How to use this page
This page explains what the measurement is for. It is educational. Your Healiam report includes the reference interval for your age and sex, and a clinician reads that result with your history, medicines, and the rest of the panel. Talk with a clinician before changing diet, supplements, or treatment because of a number on a report.
Total T3
Total T3 is part of the full panel.
No referral or insurance required.
One preventive draw covers this measurement and the rest of the Healiam panel. CLIA-certified results come back in days.