Hospital
$150+
Other Labs
$40
TestWell
$23.99
Free T4 (thyroxine) is the unbound, biologically active form of the primary thyroid hormone. It is converted to T3 (the more active form) in tissues throughout the body. Free T4 is the most reliable marker of actual thyroid hormone production because it is not affected by changes in binding proteins. Elevated Free T4 suggests hyperthyroidism, while low levels indicate hypothyroidism. This test is most useful when ordered alongside TSH for a complete picture of thyroid function, but can also be ordered standalone to monitor patients on thyroid medication.
Sample Type
Blood draw
Fasting
Not required
Results In
1–3 business days
Performed By
BioReference
1 biomarker tested
Your Free T4 (Thyroxine) results will include values for each of the 1 biomarker tested, along with reference ranges. Results are reviewed by a licensed physician before being released to your secure portal.
If any values fall outside the normal range, your report will include guidance on what that may mean and recommended next steps. You'll receive an email notification when your results are ready, typically within 1–3 business days.
Typical reference range layout
Lab reports show where your value sits relative to established reference intervals—your physician interprets this in context for you.
No fasting required. If on thyroid medication, take your dose after the blood draw.
TestWell Price
$23.99
No insurance needed · HIPAA compliant
Frequently ordered together
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Free T4 (Thyroxine)
$23.99