Total T3
The total amount of triiodothyronine in the blood, both bound and free.
| Typical reference range | 76–181 ng/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Total T3 includes T3 bound to carrier proteins and the free fraction. Most T3 comes from conversion of T4 in peripheral tissues.
Why it matters
Total T3 helps diagnose hyperthyroidism and assess its severity; it is less useful for diagnosing hypothyroidism.
What a high result can mean
High values occur with hyperthyroidism, T3 medication, and increased binding proteins from pregnancy or estrogen.
What a low result can mean
Low values occur with hypothyroidism, illness, calorie restriction, and conditions that reduce binding proteins.
What affects the result
Affected by binding proteins, illness and nutrition. Interpret with TSH and free hormones.
Units and conversion
Usually reported in ng/dL.
- From nmol/L: multiply by 65.1 to get ng/dL
Also called on lab reports
T3, Total, T3, Triiodothyronine, Triiodothyronine (T3), Triiodothyronine, Total, T3 Total
Related tests: Thyroid
This page is educational and does not replace advice from a healthcare professional.