Also known as: T3, Total (Triiodothyronine)
The short answer
Measures total triiodothyronine (T3), bound and free — the thyroid hormone that rises first in many cases of an overactive thyroid, measured from a standard blood draw. At TestWell it costs $24.99 plus a $6 lab processing fee, needs no fasting, and results post in 1–3 business days. Physician-authorized with no doctor's visit or insurance needed; draw at Quest or Labcorp.
TestWell Price
$24.99
+ $6 lab processing fee
Total T3 measures all of the triiodothyronine in your blood — the roughly 99% carried on binding proteins plus the small free fraction. T3 is the more active thyroid hormone, and in hyperthyroidism it often rises earlier and further than T4, so total T3 is part of the standard work-up when TSH is low: it distinguishes ordinary Graves' disease or toxic nodules from the less common 'T3 toxicosis' in which only T3 is elevated, and it helps gauge severity. It is less useful for diagnosing an underactive thyroid, where T3 tends to stay normal until late. Because total T3 counts protein-bound hormone, anything that changes binding proteins — pregnancy, estrogen, oral contraceptives, liver disease, some medications — shifts the result without changing thyroid function, which is why clinicians read it alongside TSH and free T4 (and sometimes free T3).
Total triiodothyronine — bound plus free T3. The classic confirmation test for an overactive thyroid, where T3 often rises earlier and further than T4 (T3 toxicosis), and part of the standard thyroid panel.
Anyone with a low or suppressed TSH being worked up for hyperthyroidism, people on thyroid medication that contains T3 (liothyronine, desiccated thyroid), or anyone completing the three-hormone picture alongside TSH and T4.
Sample Type
Blood draw
Fasting
Not required
Results In
1–3 business days · typical; varies by lab and draw day
Performed At
Quest or Labcorp
1 biomarker tested
Your T3, Total (Triiodothyronine) results will include values for each of the 1 biomarker tested, along with reference ranges. Results are reviewed by a licensed physician before being released to your secure portal.
If any values fall outside the normal range, your report will include guidance on what that may mean and recommended next steps. You'll receive an email notification when your results are ready, typically within 1–3 business days.
Typical reference range layout
Lab reports show where your value sits relative to established reference intervals—your physician interprets this in context for you. Already have results? Analyze them with your AI assistant against our physician-reviewed ranges.
No fasting required. Stop high-dose biotin supplements at least 2 days before the draw (biotin interferes with thyroid assays). If you take thyroid medication, take your dose after the blood draw.
What can throw off this result
Physician-reviewed “Before your test” pages — what each factor does, for how long, and what to do about it.
TestWell orders the same T3, Total (Triiodothyronine) the labs run for doctors' offices, so you can walk into any of these labs with our requisition — no doctor's visit, a licensed physician authorizes the order, and most patient service centers take walk-ins. The table shows each lab's own test code, the name printed on the requisition, what the lab charges on its own consumer site, and the price through TestWell at that lab (plus one $6 fee per order).
| Lab | Test code | On the requisition | Lab's own site | Through TestWell |
|---|---|---|---|---|
| Quest Diagnostics | test code 859 | “T3, Total (Triiodothyronine)” | not sold direct | $24.99 + $6 |
| Labcorp | test no. 002188 | “T3, Total (Triiodothyronine)” | not sold direct | $29.99 + $6 |
| BioReference (New York & New Jersey) | test code 0150-3 | “T3, Total (Triiodothyronine)” | n/a | $24.99 + $6 |
You choose the lab at checkout; the requisition is written for that lab and arrives by email within minutes. New York and New Jersey orders draw at BioReference. Lab-direct prices are read from the labs' public pages and re-checked regularly.
Where to get it near you: patient service centers by state and city · search by ZIP code
A Total T3 (Triiodothyronine) test costs $24.99 at TestWell — $30.99 all-in, since the $6 lab processing fee is charged once per order and there is no draw or physician fee. Hospital outpatient labs typically bill around $120.00 self-pay. With insurance you pay your plan's negotiated rate against your deductible; TestWell's price is fixed before the draw and HSA/FSA-eligible.
| Where you order | Price | One test, all-in | Notes |
|---|---|---|---|
| TestWell (drawn at Quest) | $24.99 | $30.99 | Includes the one $6 lab processing fee, charged once per order |
| TestWell (drawn at Labcorp) | $29.99 | $35.99 | Labcorp's own cost for this test is higher; same order, same portal, same physician review |
| TestWell (drawn at BioReference — New York & New Jersey) | $24.99 | $30.99 | New York and New Jersey orders route to BioReference; Quest Health and Labcorp OnDemand don't take self-ordered draws in those states |
| Hospital outpatient lab, self-pay (typical) | $120.00 | $120.00 | Reference figure; hospital charges vary widely by facility and are often higher |
Lab test codes: Quest test code 859 · Labcorp test no. 002188 · BioReference code 0150-3. Competitor prices are read from the linked public pages and re-checked regularly; the labs' sites may add taxes or change prices without notice.
Compare more: Quest Diagnostics price list · Labcorp price list · Quest vs Labcorp · Lab test price checker
It measures all the triiodothyronine in your blood — the roughly 99% riding on carrier proteins plus the small free fraction — in ng/dL (Quest test 859, Labcorp 002188). T3 is the active thyroid hormone, and in an overactive thyroid it typically rises before and beyond T4, so total T3 is the test that confirms hyperthyroidism when TSH is low. It's also how clinicians monitor T3-containing thyroid medication. $24.99 here, no fasting, results in 1–3 business days.
Total T3 for a suspected overactive thyroid or to monitor liothyronine / desiccated thyroid — it's the better-standardized assay and what the hyperthyroidism guidelines use. Free T3 for the "am I converting T4 into T3" question in someone with a normal TSH, because it isn't skewed by the carrier proteins that estrogen, pregnancy, the pill and liver disease change. If you're unsure, the Thyroid Panel with TSH carries TSH, total T4 and total T3 together.
High total T3 with a low TSH confirms hyperthyroidism (Graves' disease, a toxic nodule, too much thyroid medication); high total T3 with a normal TSH is usually a carrier-protein effect — estrogen or pregnancy raises the binding proteins — rather than real excess, which is where free T3 helps. Low total T3 with normal TSH and T4 is most often "non-thyroidal illness" or the body conserving energy during fasting, crash dieting or hard training, and tends to recover on its own; low T3 with a high TSH is part of an underactive thyroid.
Total T3 (Triiodothyronine) test results are typically ready in 1–3 business days after your draw at Quest or Labcorp. TestWell emails you the moment they post, and your results dashboard shows each marker against its reference range with a plain-English explanation.
No, fasting is not required for a Total T3 (Triiodothyronine) test — you can eat normally and book any time of day. Stop high-dose biotin supplements at least 2 days before the draw (biotin interferes with thyroid assays). If you take thyroid medication, take your dose after the blood draw.
Biotin supplements, oral contraceptives and estrogen and ashwagandha and thyroid-support supplements can change a Total T3 (Triiodothyronine) test result without anything being wrong. Biotin supplements can falsely raise T3, Total — stop biotin ≥72 hours before the draw. Oral contraceptives and estrogen can raise T3, Total — use TSH and Free T4 — free levels are not affected. Ashwagandha and thyroid-support supplements can raise T3, Total — interpret with the supplement in mind; stop before a repeat draw only with the clinician's agreement. Each is explained on our physician-reviewed "Before your test" pages; when one applies, remove it and retest.
Order the Total T3 (Triiodothyronine) test online from TestWell for $24.99 (plus a $6 per-order lab processing fee) — no doctor's visit, referral or insurance needed. A licensed physician authorizes the order, then you walk into any Quest or Labcorp patient service center near you for the draw (the lab locator on our site lists the closest ones by ZIP code), and results arrive in 1–3 business days.
The Total T3 (Triiodothyronine) test is Quest Diagnostics test code 859, Labcorp test number 002188, BioReference code 0150-3. TestWell orders it under those codes for $24.99 at Quest, Labcorp or BioReference — no doctor's visit or insurance required, results in 1–3 business days. Codes verified against the labs' catalogs in 2026.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
TestWell Price
$24.99
+ $6 lab processing fee at checkout
No insurance needed · HIPAA compliant
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