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T4 Free

Alternative Name:

Free T4, FT4

Clinical Utility:

Thyroxine (T4) and Triiodothyronine (T3) and thyroid stimulating hormone (TSH) are used to assess thyroid function. Most T4 and T3 circulate bound to protein but a small portion (free T4) circulates unbound and is the active form of thyroxine. Since free T4 is not affected by levels of protein it is not subject to fluctuations due to varying levels of protein.


1 mL SST Tube

Collection Instructions:

Fill tube, invert gently 5 times, label with patient name, let stand for minimum of 30 minutes, maximum of 1 hr, spin for 10-15 minutes

Storage Instruction:


Turnaround Time:

1 days

CPT Code:

84439 (1)