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Free Thyroxine (FT4) (Free T4) from Marek Health

Labbrary Test GradeUseful
Your Fit Score
Not calculated

Answer five questions to see how this panel matches your goals, budget, collection preferences, access, and support needs.

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Labbrary's review, Fit Score, and basic comparison are free. The provider's panel, shipping, collection, clinician review, and other services are separate. About 2 minutes. No account required.

Measure free T4, the unbound thyroid hormone available to your tissues, as part of an assessment of thyroid function.

Current price
$13 $23 with fees
Sample
Blood
Turnaround
14 days
Access
Direct Lab, Lab Visit, Order Online
Evidence & Key Facts
Source collectedLast source check September 9, 2026

Evidence basis. This named result reflects the sources and verification evidence listed on this page as of the date shown.

Best for

Thyroid

Standout strength

This blood test measures free thyroxine, or FT4, the unbound portion of T4 available to body tissues.

Important watch-out

Marek adds a $10 venipuncture fee to orders of $199 or less and waives it on orders over $199. No additional payment is required at the lab. Lab sales are final and non-refundable.

Free Thyroxine (FT4) (Free T4) from Marek Health
Labbrary Test GradeUseful
Your Fit Score
Not calculated

Answer five questions to see how this panel matches your goals, budget, collection preferences, access, and support needs.

Calculate my fit

Labbrary's review, Fit Score, and basic comparison are free. The provider's panel, shipping, collection, clinician review, and other services are separate. About 2 minutes. No account required.

Measure free T4, the unbound thyroid hormone available to your tissues, as part of an assessment of thyroid function.

Current price
$13 $23 with fees
Sample
Blood
Turnaround
14 days
Access
Direct Lab, Lab Visit, Order Online
Evidence & Key Facts
Source collectedLast source check September 9, 2026

Evidence basis. This named result reflects the sources and verification evidence listed on this page as of the date shown.

Best for

Thyroid

Standout strength

This blood test measures free thyroxine, or FT4, the unbound portion of T4 available to body tissues.

Important watch-out

Marek adds a $10 venipuncture fee to orders of $199 or less and waives it on orders over $199. No additional payment is required at the lab. Lab sales are final and non-refundable.

Labbrary+

The Test Grade. The Reason Behind It.

Potentially useful for the right buyer, with meaningful evidence, coverage, transparency, access, cost, terms, or privacy tradeoffs to review.

A lower grade does not mean a panel is a bad personal fit. Your Fit Score can be higher when its purpose, price, sample, access, or support matches what you need.

Explore the Full Methodology
Labbrary Test GradeUseful

Next step

Check the panel or research the provider

Prices, availability, and ordering requirements can change. Confirm the current details before purchasing.

View Exact Panel on Provider SiteView Marek Health profile

Scope, both directions

Inside the Panel. Beyond the Name.

Named measurements

  • Free Thyroxine (FT4)

Measured categories and focus areas

  • Thyroid

Important limits and omissions

  • Free thyroxine is the named measurement. High-dose biotin interference is disclosed, but the exact analytical method, performing laboratory, assay validation and specimen-handling requirements remain unassessed.
  • The named scope is free T4 alone. TSH, free T3 and thyroid antibodies are not listed as included. Sufficiency for an individual thyroid evaluation remains unassessed.
  • Results are emailed when available. Guided Optimization is a separate program with treatment eligibility requirements. An included consultation, individual interpretation service, actual sample report, reference-range explanation and follow-up plan have not been established for this test purchase.
  • Comparative value and clinical data or specimen privacy have not been fully assessed.

Pre-Buy Audit · Labbrary+

1broader panel with a lower listed price lists every biomarker on this one.

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Included with Labbrary+. Members see each panel by name and listed price, and can audit them in one click.

Counted among one-time lab-draw listings with a published price, matched by published biomarker names. That doesn’t mean the tests are equivalent. Updated October 2, 2026.

The full breakdown

Eight Dimensions.
One Named Result.

Open any row for the reasoning and evidence behind the named result.

Seller is Marek Diagnostics; the ordering clinician is Marek-arranged (provider reviews and approves test requests; no buyer clinician visit required) where stated. Collection route is the Quest Diagnostics laboratory system. A Quest draw location or the Marek relationship does not prove the exact performing facility, the assay method, or offer-specific analytical performance, which remain unpublished. Limitation: Seller is Marek Diagnostics; the ordering clinician is Marek-arranged (provider reviews and approves test requests; no buyer clinician visit required) where stated. Collection route is the Quest Diagnostics laboratory system. A Quest draw location or the Marek relationship does not prove the exact performing facility, the assay method, or offer-specific analytical performance, which remain unpublished.

Exact named measurement scope per the product page title and description. Limitation: No additional limitation was recorded in the authority row.

Named analytes per the exact offer; panel boundaries per the product page. Limitation: No additional limitation was recorded in the authority row.

Result delivery format partially documented. Limitation: No additional limitation was recorded in the authority row.

Exact price, purchase route, and ordering model on the product page; performing lab assignment unpublished. Limitation: No additional limitation was recorded in the authority row.

Online ordering with provider-approved test requests; Quest collection; state restrictions apply. Limitation: No additional limitation was recorded in the authority row.

Exact-offer price on the product page; refund and draw-fee terms per shared policies. Limitation: No additional limitation was recorded in the authority row.

Shared Marek privacy policy governs order data; specimen and result retention unresolved. Limitation: No additional limitation was recorded in the authority row.

What it asks of you

Sample and fulfillment journey

Order

Confirmed

Order Free Thyroxine (FT4) (Free T4) online for $13 before any checkout fees. Healthcare-provider review and approval is arranged without an office visit.

Panel-specific source · Source dated September 9, 2026

Collect

Confirmed

Order online for healthcare-provider review and approval, then provide a blood sample at a Quest location. No healthcare-provider office visit is required. Confirm preparation and collection instructions for this exact test. High-dose biotin can interfere with this test. Stop biotin supplementation at least 72 hours before the draw, following the ordering clinician's instructions. Confirm any other collection preparation.

Panel-specific source · Source dated September 9, 2026

Lab

Confirmed

Results typically arrive within 14 business days. Approximately two weeks is a general estimate that varies with test size and complexity; it is not a guaranteed calendar-day deadline. The exact laboratory performing the assay has not been independently identified.

Panel-specific source · Source dated September 9, 2026

Report

Partially confirmed

Results are emailed when available. Guided Optimization is a separate program with treatment eligibility requirements. An included consultation, individual interpretation service, actual sample report, reference-range explanation and follow-up plan have not been established for this test purchase.

Panel-specific source · Source dated September 9, 2026

Under the hood

Follow the Evidence.

Every published claim should trace to a dated source. Missing evidence remains visible instead of being filled with assumptions.

Source 1Recorded for this record. Last source check September 9, 2026.View source
Source 2Recorded for this record. Last source check September 9, 2026.View source
Source 3Recorded for this record. Last source check September 9, 2026.View source
Source 4Recorded for this record. Last source check September 9, 2026.View source
Source 5Recorded for this record. Last source check September 9, 2026.View source
Source 6Recorded for this record. Last source check September 9, 2026.View source
Source 7Recorded for this record. Last source check September 9, 2026.View source
Source 8Recorded for this record. Last source check September 9, 2026.View source

True total cost

The Price. Plus the Details.

Pricing for Free Thyroxine (FT4) (Free T4)
ItemCurrent disclosed priceNote
Panel$13Verify the checkout total, shipping, and collection fees before ordering.
Venipuncture fee+ $10Per order, added at checkout. Checked October 1, 2026. Source
Total at checkout$23Listed price plus the required fees above, before tax and any optional services.
HSA/FSA paymentNot confirmedHSA/FSA payment eligibility has not been confirmed from provider documentation.
Optional servicesNot confirmedClinician review, subscriptions, and retesting discounts are listed only when documented.

Price status. This record shows disclosed pricing. Checkout costs can change and should be verified before purchase.

Your data

Your Data. Your Questions.

Privacy details are scored only when source documentation is available. Unconfirmed retention, deletion, research use, or marketing practices remain unconfirmed.

Reading the labels

What Has Been Checked?

Source collected

Evidence labels stay separate from the Test Grade. They show how much source support exists for the evaluation.

The balance

The Strengths. The Tradeoffs.

Strengths

  • This blood test measures free thyroxine, or FT4, the unbound portion of T4 available to body tissues.
  • Order online for provider approval and blood collection at Quest.
  • The lab requisition is valid for six months from purchase.

Watch-outs

  • Marek adds a $10 venipuncture fee to orders of $199 or less and waives it on orders over $199. No additional payment is required at the lab. Lab sales are final and non-refundable.
  • Eligible US residents need a valid US driver license or state-issued ID. Hawaii and US territories are excluded, and orders are unavailable to residents of New York, New Jersey and Rhode Island. Massachusetts buyers should confirm that the collection site accepts the order before paying.
  • Results typically arrive within 14 business days. Approximately two weeks is a general estimate that varies with test size and complexity; it is not a guaranteed calendar-day deadline.
  • Free thyroxine is the named measurement. High-dose biotin interference is disclosed, but the exact analytical method, performing laboratory, assay validation and specimen-handling requirements remain unassessed.
  • The named scope is free T4 alone. TSH, free T3 and thyroid antibodies are not listed as included. Sufficiency for an individual thyroid evaluation remains unassessed.
  • Results are emailed when available. Guided Optimization is a separate program with treatment eligibility requirements. An included consultation, individual interpretation service, actual sample report, reference-range explanation and follow-up plan have not been established for this test purchase.
  • High-dose biotin can interfere with this test. Stop biotin supplementation at least 72 hours before the draw, following the ordering clinician's instructions. Confirm any other collection preparation.

Take it with you

The Test Truth Card

The key facts from this review in one compact card.

Same biomarkers, other sellers

Other Ways to Buy This Test.

3 other listings in the Labbrary catalog publish this exact biomarker list, with a lab draw.

Free Thyroxine (Free T4) Blood Test

Mito Health

Useful

Measures unbound thyroxine to help interpret thyroid function alongside TSH, follow up an abnormal result or monitor treatment. Order this single-marker test online for a participating laboratory blood draw.

Price
$5.52
Turnaround
2 days
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+

Free T4 (Thyroxine), Dialysis Blood Test

Mito Health

Useful

Measures free thyroxine using equilibrium dialysis to help investigate thyroid results affected by abnormal binding proteins or other assay limitations. Order online for a participating laboratory blood draw.

Price
$16.79
Turnaround
11 days
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+

Free T4

Everlywell

Useful

Measures Free T4 using a blood sample collected at a participating location. Order online, complete clinician review and access results through your account.

Price
$43
Turnaround
Not confirmed
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+

Listed prices from the Labbrary catalog. Some sellers add fees at checkout, so compare the total before you pay. Updated October 2, 2026.

Keep deciding

Thyroid Peroxidase (TPO) Ab

Marek Health

Useful

Check thyroid peroxidase antibodies in blood with a biotin preparation warning, ordered online for Quest collection.

Price
$15
Turnaround
14 days
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+

Triiodothyronine, Free (Free T3) Blood Test

Mito Health

Useful

Measures unbound triiodothyronine to help evaluate thyroid function alongside TSH and free T4, particularly when hyperthyroidism is suspected. Order online for a participating laboratory blood draw.

Price
$10.59
Turnaround
2 days
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+

Free T3

Everlywell

Useful

Measures Free T3 using a blood sample collected at a participating location. Order online, complete clinician review and access results through your account.

Price
$43
Turnaround
Not confirmed
See Labbrary reviewView Exact Panel on Provider Site
Labbrary+
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Verification History

September 9, 2026Recorded source date.Source collected

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