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T4 Free

Message
This test can be ordered by providers but it is also added as a reflex test by the Lab if the TSH is less than 0.35 OR greater than 5.00.


Test Code
THYROID T4 FREE(FT4)


Alias/See Also
Free T4
Chemistry


Preferred Specimen
Gold Top Tube


Transport Temperature
Refrigerate


Specimen Stability
Refrigerated (2-8°C): 6 days
Frozen (-20°C or colder): > 6 days
If testing delayed > 24 hours remove from clot/gel


Methodology
Chemiluminescent microparticle immunoassay

Setup Schedule
M-F


Report Available
TAT 1 - 7 days


Reference Range
0.6 - 1.6 ng/dL


Clinical Significance
For diagnosis of hypothyroidism and hyperthyroidism.


Performing Laboratory
Test performed at West Roxbury Chemistry Lab
Contact: Jonathan Dryjowicz-Burek 857-203-5973


Last Updated: November 21, 2025


The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.