Hospital Lab
$150
cash pay
Other Labs
$40
+ lab fees
TestWell
$23.99
+ $6 lab fee
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.
Measures the unbound (active) form of thyroxine. Pairs with TSH to confirm thyroid dysfunction and distinguish primary from central causes.
Anyone with abnormal TSH, fatigue, weight changes, hair thinning, cold intolerance, or other symptoms of thyroid disease. Monitoring patients on levothyroxine or methimazole therapy.
Sample Type
Blood draw
Fasting
Not required
Results In
1–3 business days
Performed At
Quest or Labcorp
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.
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.
No fasting required. If on thyroid medication, take your dose after the blood draw.
TestWell Price
$23.99
+ $6 lab processing fee at checkout
No insurance needed · HIPAA compliant
Better value: the Advanced Thyroid Panel
Save $88.94This test is part of the Advanced Thyroid Panel — 7 tests · 8 biomarkers for $129.99, $88.94 less than à la carte.
$129.99$218.93
7 tests · 8 biomarkers
Frequently ordered together
Customers who ordered Free T4 (Thyroxine) also added these for a more complete health picture.
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Free T4 (Thyroxine)
$23.99