Total T3 optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for Total T3:
- Optimal 100 – 180 ng/dL (1.5 – 2.8 nmol/L); sufficient 80 – 200 ng/dL (1.2 – 3.1 nmol/L); out of range below 80 or above 200 ng/dL.
Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| ng/dL | 100 – 180 | 80 – 200 | below 80 or above 200 |
| nmol/L | 1.5 – 2.8 | 1.2 – 3.1 | below 1.2 or above 3.1 |
| pg/mL | 1,000 – 1,800 | 800 – 2,000 | below 800 or above 2,000 |
What the evidence says
The acceptable band of 80 to 200 ng/dL is the adult reference interval of Mayo Clinic Laboratories. Intervals differ by assay: Labcorp reports 71 to 180 ng/dL, so the laboratory's own interval takes precedence. The optimal band of 100 to 180 ng/dL is a functional target with no published study or guideline behind it. Total T3 follows binding proteins and is not a reliable marker of hypothyroidism; it falls in illness and with amiodarone.
Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.
Sources
- T3 (Triiodothyronine), Total, Serum — Mayo Clinic Laboratories, 2026 · Laboratory / reference-interval sourceAdult reference values (20 years and older) 80 to 200 ng/dL; values above 200 ng/dL in adults are described as consistent with hyperthyroidism or raised binding proteins. This is Sera's sufficient band exactly.
- Triiodothyronine (T3) — Labcorp, 2026 · Laboratory / reference-interval sourceReference range for ages over 10 years 71 to 180 ng/dL by electrochemiluminescence immunoassay. Shows the interval is assay-dependent: both edges sit below Sera's 80 and 200.
What Total T3 measures
The total amount of T3 in your blood, both the bound and the free forms.
Gives useful context alongside Free T3 and helps show your overall T3 status.