Thyroxine (T4) Antibody
Explains a T4 result that does not match TSH or your symptoms by checking for antibodies that distort the assay.
Consider this test if:
- A T4 result that does not match your TSH or your symptoms
- Elevated T4 alongside a normal or elevated TSH with no clear explanation
- Known autoimmune thyroid disease and inconsistent or unstable T4 readings
- A clinician is ruling out assay interference before changing thyroid treatment
- HSA/FSA eligible
- Results delivered to your dashboard · Reviewed by a real clinician
- Drawn at a CLIA/CAP-accredited lab near you ·
Pre-test considerations
No fasting required. Biotin supplements, heterophilic antibodies, and other interfering substances can independently distort thyroid immunoassays, so note any biotin use and pause high-dose biotin for several days before testing if advised. This test is most informative when paired with the discordant T4 and TSH results that prompted it.
Video consult with your Care Team
A 1:1 call to discuss your health.
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What this test is for
This test detects autoantibodies to thyroxine (T4), known as thyroid hormone autoantibodies, which interfere with the immunoassays used to measure T4. These antibodies compete with the assay's own T4 antibodies, producing a falsely high or low T4 reading that does not fit the clinical picture. They appear in some healthy people but are more common in autoimmune thyroid disease, and the interference can be transient or persist for years. The test is used to troubleshoot a specific problem: a T4 level that is discordant with TSH, other thyroid results, or how you actually feel (for example, an elevated T4 with a normal or elevated TSH). It pinpoints whether antibody interference, rather than true thyroid dysfunction, explains the mismatch, after which clinicians can switch to an interference-resistant method.
This is a troubleshooting test, not a thyroid status test. For routine thyroid evaluation, free T4 and TSH measure hormone level and pituitary signaling; this antibody test is the right marker only when those numbers do not add up.
- Specimen
- Serum
- Measures
- Presence / threshold
What you'll learn
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Insights that connect the dots. A clinician reads your whole picture, not one result in isolation, connecting family history, past results, and lifestyle into clear next steps.
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Your personalized action plan. Nutrition, supplements, and training in one clinician-reviewed protocol, updated as your results change.
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Track your trends. Upload results from any lab and see each biomarker trend over time, so you know what is working.
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Never miss a recheck. Mito tells you what is worth retesting and when, then reminds you so nothing slips.
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 Fast, dashboard-delivered results
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
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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.
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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.
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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.
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Without membership
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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. It is never a profit on the test itself. Mito makes its money on the $9 membership, not on marking up your tests. Membership is $9 per month, and any applicable lab order or draw fee is itemized before you pay.
Where do I get tested?
Choose an available partner lab at checkout. If your cart contains multiple blood tests, Mito helps consolidate the eligible tests at one lab when possible. At-home kits and scans follow the collection or appointment process shown on their product page.
Is this eligible for HSA/FSA?
Yes. Eligible tests can be paid for with an HSA or FSA card at checkout.
When will I get my results?
Your results appear in your Mito dashboard after the laboratory completes processing. A clinician then reviews them before your analysis and personalized action plan are finalized. Timing varies by test, and specialty assays and at-home kits may take longer.
Do I need a physician's order?
No. Mito provides the laboratory order when one is required, so you do not need to arrange a separate physician visit before purchasing.
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