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.
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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.
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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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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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.
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