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T4, Free

Source Blood
Mnemonic

FT4
If only T4 is indicated on the requisition, order Free T4 (FT4).

Specimen Requirements

1 x 3 mL or 4.5 mL light green (mint) top PST tube.  Gold top SST tube also acceptable.

0.5 mL plasma or serum

Minimum Whole Blood Volumes for Microcollections

Collection can be combined in one 5 mL PST or SST tube with other thyroid tests.

Specimen Handling
Additional Information  If FT4 test has been ordered with additional wording such as "equilibrium" or "dialysis", see T4 (Thyroxine), Free by Equilibrium Dialysis (FT4D).
Testing Location Chemistry-DSC
Testing Frequency Daily
Alternate Name(s) Free T4; Thyroxine, Free
Reference Interval 10.0 - 25.0 pmol/L