T4, Free CPT: 84439
Expected Turnaround Time
Within 1 day
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
0.3 mL (Note: This volume does not allow for repeat testing.)
Red-top tube or gel-barrier tube
If a red-top tube is used, transfer separated serum to a plastic transport tube.
Heparin has been reported to have in vivo and in vitro effects on free T4 assay. Hence samples should not be collected during or soon after the administration of this anticoagulant.
To help evaluate thyroid gland function; to help diagnose thyroid disease; to monitor effectiveness of thyroid treatment; sometimes a free T4 is used to help diagnose congenital hypothyroidism in newborns.
When you have signs and symptoms of thyroid disease and/or an enlarged thyroid (goiter) or when you have a thyroid nodule (a small lump on the thyroid gland that may be solid or fluid-filled cyst), usually after an abnormal result on a TSH test; when you are being treated for a thyroid disorder.
A blood sample drawn from a vein in your arm or from pricking the heel of an infant.
None needed; however, certain medications, multivitamins and supplements can interfere with the free T4 test, so tell your healthcare provider about any prescribed or over-the-counter drugs and/or supplements that you are taking. If you take thyroid hormone as treatment for thyroid disease, it is recommended that your blood sample be drawn before you take your dose for that day. Acute illness may affect thyroid testing results. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness.