Free T3 levels: what's normal, high and low
The active, unbound form of T3 — the most metabolically active thyroid hormone.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
The short answer
Free T3 is measured with a standard blood draw; no fasting is needed. A typical reference range is 2.00 – 4.40 pg/mL. At TestWell it's $30.99 all-in as Free T3 (Triiodothyronine), results in 1–3 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis.
- Units
- pg/mL
- Sample
- Blood draw
- Fasting
- Not required
- Results
- 1–3 business days
- Price
- $30.99
- Labs
- Quest or Labcorp · BioReference in NY/NJ
Free T3 Reference Range
These are the typical adult reference ranges used by major US labs. Your report will include the specific range used by the lab that processed your sample.
| Population | Range |
|---|---|
| age 18+ | 2.00 – 4.40 pg/mL |
Reference ranges are educational. Always interpret your result with the specific range printed on your lab report and discuss anything outside the range with a clinician.
How do you get a Free T3 test?
Order online, a licensed physician reviews the requisition, and you walk into a nearby lab for the draw. Free T3 is available on its own or inside these panels — panels cost less per marker when you want the fuller picture.
| Option | Includes | Price |
|---|---|---|
| Free T3 (Triiodothyronine) | This marker only | $30.99 |
| Essential Thyroid Panel | 3 tests | $79.99 |
| Hashimoto's Thyroid Panel | 3 tests | $97.99 |
| Complete Thyroid Panel | 4 tests | $109.99 |
| Advanced Thyroid Panel | 7 tests | $129.99 |
Quest vs. Labcorp for Free T3: which lab should you pick?
Both are CLIA-certified national labs and the result is clinically equivalent, so pick whichever location is closer. Your report will print that lab's own reference range, which can differ slightly from the table above.
| Lab | Available | Price |
|---|---|---|
| Quest Diagnostics | Yes | $30.99 |
| Labcorp | Yes | $30.99 |
| BioReference (NY & NJ) | Yes | $32.99 |
Need help choosing a location? Use the lab finder to see draw sites near your ZIP.
Related Thyroid biomarkers
Markers commonly tested alongside Free T3.
Frequently asked
No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor.
Ready to test your free t3?
Order in two minutes, get physician-approved, and visit a lab the same day. Starts at $30.99.