Thyroxine, Free T4, Free T-4, Tetraiodothyronine
Thyroxine (T-4), Serum
Thyroxine, Free (fT4)
*THIS TEST IS AVAILABLE FOR PEDIATRIC PATIENTS
If Thyroxine, Free (Free T-4) testing is requested for an adult please order in-house test code T4-FREE.
Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Serum must be separated from cells within 45 minutes of venipuncture. Send serum in a plastic transfer tube. FREEZE.
Plasma or whole blood samples received.
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Testing is performed at Esoterix Endocrinology Lab (a division of LabCorp).