Thyroid Panel (Total T4, T3 Uptake, TSH, Free Thyroxine Index)
A four-part read on thyroid function, from the pituitary signal down to circulating thyroid hormone.
Consider this test if:
- Fatigue, weight change, cold or heat intolerance, hair loss, or brain fog with no clear cause
- Palpitations, tremor, anxiety, or unexplained weight loss suggesting an overactive thyroid
- Setting a thyroid baseline or rechecking after a borderline TSH
- Adjusting or monitoring thyroid hormone replacement
- A family history of thyroid disease and wanting a fuller picture than TSH alone
- HSA/FSA eligible
- Typical results in 1 day · Reviewed by a real clinician
- Drawn at a CLIA/CAP-accredited lab near you ·
Pre-test considerations
No fasting required. Biotin supplements can interfere with thyroid immunoassays, so stop high-dose biotin for about 48 hours before the draw. Recent illness, pregnancy, estrogen, and some medications shift T4 and binding proteins, which is partly why T3 uptake and the FTI are used to correct for binding.
Video consult with your Care Team
A 1:1 call to discuss your health.
What members say on Trustpilot
What this test is for
This panel evaluates thyroid function using TSH, total T4, T3 uptake, and the calculated free thyroxine index (FTI). TSH is the pituitary signal that drives the thyroid, and it is the most sensitive screening marker; total T4 measures circulating thyroxine, while T3 uptake corrects for protein binding so the FTI can estimate how much T4 is actually free and active. Together they help sort out hypothyroidism (fatigue, weight gain, cold intolerance, constipation, hair loss, brain fog) and hyperthyroidism (weight loss, palpitations, heat intolerance, anxiety, tremor). A normal TSH alone rules out most primary thyroid disease, so the added T4 and FTI are most useful when TSH is abnormal or symptoms persist; this panel does not detect T3 thyrotoxicosis, which needs free or total T3.
This version includes TSH, which makes it a reasonable standalone thyroid workup. If your question is T3-driven overactivity, the panel that adds total T3 is the better fit; if you already have a recent TSH and only need the hormone estimate, the T4-plus-T3-uptake panel without TSH covers that.
Biomarkers tested
Includes 4 biomarkers
The free T4 index is a calculated estimate of active, unbound thyroxine, correcting for the binding proteins that can distort total T4 readings and give a cleaner read on how much thyroid hormone is actually available to your tissues. Doctors use it as a backup or alternative to direct free T4 when protein levels are shifting, from pregnancy, oral estrogen, liver disease, or acute illness. Low values point toward hypothyroidism, with fatigue, weight gain, cold intolerance, hair thinning, and constipation, while high values point toward hyperthyroidism, with anxiety, palpitations, heat intolerance, and unintended weight loss, and either result is best interpreted alongside TSH.
- Specimen
- Serum or plasma
- Method
- Calculated
- Measures
- Mass concentration
T3 resin uptake doesn't measure thyroid hormone directly. It measures how much binding capacity is left on thyroxine-binding globulin (TBG), the protein that carries thyroid hormone through your blood, by seeing how much added radiolabeled T3 gets picked up by a resin instead of binding to TBG. Doctors pair it with total T4 or T3 to calculate a free thyroxine index, which corrects for conditions like pregnancy, estrogen use, or liver disease that raise or lower TBG and can otherwise make thyroid results look abnormal when actual hormone activity is normal, useful when thyroid symptoms like fatigue, weight change, or temperature sensitivity don't match your TSH.
- Specimen
- Serum or plasma
- Measures
- Number fraction (%)
Total T4 measures all the thyroxine circulating in your blood, both the small free fraction that acts on cells and the larger portion bound to carrier proteins. Because binding proteins shift with pregnancy, estrogen, and liver or kidney conditions, total T4 can rise or fall without your actual thyroid function changing, which is why it's usually read alongside TSH and free T4 rather than alone. It's most useful for catching those binding-protein effects and rounding out the picture when TSH looks off but the cause isn't yet clear.
- Specimen
- Serum or plasma
- Measures
- Mass concentration
TSH is the pituitary's signal to the thyroid, rising when it senses too little thyroid hormone in circulation and falling when there's too much. High TSH points to an underactive thyroid, often behind fatigue, weight gain, cold intolerance, constipation, dry skin, and low mood. Low TSH points to an overactive thyroid, showing up as anxiety, racing heart, weight loss, heat intolerance, or sleep trouble, and it's the single most sensitive marker for catching thyroid dysfunction before it fully unravels your energy, weight, and cycle.
- Specimen
- Serum or plasma
- Measures
- Concentration
What to expect
- 1 Book instantly
Click, book, done. Choose a convenient lab location near you. Transparent, up-front pricing.
- 2 Quick lab visit
Testing to fit your busy schedule, usually 15 minutes or less. Walk-in and appointments available.
- 3 Typical results in 1 day
Your results post straight to your dashboard as soon as the lab completes them.
- 4 Expert guidance
Included with Mito membership. A clinician reviews your results and your personalized action plan follows, with clear next steps.
Everything your health needs,
in one membership
-
Every test at our cost
Members pay our cost on every test, with lab fees passed straight through. The full receipt is itemized, never padded.
-
Continuous tracking, all in one place
Upload past labs and watch your trends over time. Every marker and visit lives in one longitudinal record, so all your care stays together.
-
Year-round clinician support
Text anytime and get clinician-reviewed answers. When you want to go deeper, 1:1 consultations are available at affordable rates.
All for $9/month
Order any test or consult without joining. For $9/month, members unlock member prices, trend tracking, and year-round clinician guidance.
Mito Membership
$9 /mo
cancel anytime
Without membership
$0
pay as you go
At-cost pricing on labs, scans, and more
Priority turnaround on your results
On-demand clinician consults when you need guidance
Personalized action plans across supplements, exercise, nutrition, and sleep
AI health coaching to help you act on your results
Year-round medical support, with in-chat clinician escalation
All your health records in one personal vault, with trends and biological age tracking
Early access to new diagnostics and product releases
More tests to consider
Loading essentials…
Frequently asked questions
View all FAQsHow does pricing work?
Every test shows the member price next to the standard non-member price, so you can see what membership saves you. The member price is our cost — covering the lab and what it takes to run the service — never a profit on the test itself; Mito makes its money on the $9 membership, not on marking up your tests. Membership is $9/mo, and you still pay the lab’s order fee. Prices are itemized before you pay, with no hidden fees.
Where do I get tested?
Choose a partner lab (Quest, Labcorp, or BioReference) at checkout. If your cart spans multiple tests, we consolidate the whole order onto a single lab so you only make one visit.
Is this eligible for HSA/FSA?
Yes. This test is HSA/FSA eligible, and you can pay with your HSA/FSA card at checkout.
When will I get my results?
Your results post to your dashboard once your lab completes them, then a clinician reviews them and your full analysis and personalized action plan (with clear next steps) follow. Turnaround varies by test: specialty assays and at-home kits take longer, and each test shows its expected turnaround before you buy.
Do I need a doctor’s order?
No. Mito provides the lab order for you, so you can book and get tested without a separate doctor visit.
Recently viewed
Loading essentials…