Direct measurement of FT3 by equilibrium dialysis, high-pressure liquid chromatography, and tandem mass spectrometry (ED-HPLC/MS-MS) provides enhanced accuracy over commonly used analog (automated) methods and is not affected by clinical conditions that impact protein binding capacity.
Free T3 (FT3) is the active form of thyroid hormone that regulates metabolic rate, energy production, and heat generation. This test uses dialysis and mass spectrometry for precise measurement, avoiding interference from protein-binding variations that can distort results from standard automated methods. It's ordered when thyroid dysfunction is suspected or when standard thyroid tests are inconclusive.
Thyroid function directly affects aerobic capacity, recovery speed, and metabolic efficiency—all critical for endurance and strength athletes. Low FT3 can impair VO₂ max, slow recovery, and increase injury risk; high FT3 may cause excessive fatigue and weight loss. This high-accuracy test is particularly useful for athletes with unexplained fatigue, performance plateaus, or recovery issues, since standard thyroid screening can miss subtle dysregulation.
Turnaround Time
6 days (up to 10 days)
Order online
Choose your lab and check out. We send your lab requisition automatically — no doctor visit needed.
Get your sample collected
Visit a lab service center near you for a quick blood draw (or book at-home phlebotomy where available).
See your results
Your results land in your Insider portal, ready to review and act on — that easy.
Your price
$105.00$190
1.8× less than retail
Versus the typical direct-to-consumer retail price for this test (illustrative — consumer prices vary by provider and region).
$105.00
Peer-reviewed sources supporting the educational content on this page.
Direct measurement of FT3 by equilibrium dialysis, high-pressure liquid chromatography, and tandem mass spectrometry (ED-HPLC/MS-MS) provides enhanced accuracy over commonly used analog (automated) methods and is not affected by clinical conditions that impact protein binding capacity.
Free T3 (FT3) is the active form of thyroid hormone that regulates metabolic rate, energy production, and heat generation. This test uses dialysis and mass spectrometry for precise measurement, avoiding interference from protein-binding variations that can distort results from standard automated methods.
The T3, Free, Dialysis, LC/MS-MS test starts at $105.00 at Labcorp. No doctor's visit and no insurance needed; we do not bill insurance. Fitomics Insider members pay from $95.00.
Results for the T3, Free, Dialysis, LC/MS-MS test are typically ready about 6 days after your draw, and up to 10 days for some samples. Your results land in your Insider portal.
No. When you order the T3, Free, Dialysis, LC/MS-MS test from Fitomics Research Labs, a licensed physician in our 50-state network reviews and signs your requisition after checkout, and it lands in your portal and inbox. Then visit any Labcorp, Quest, or BioReference patient service center for your draw; results post to your Insider portal.
Looking for something else? Browse every test by category.
