Most thyroxine in the bloodstream is bound to proteins, and only the free fraction is biologically active. Direct measurement of free T4 avoids the influence of binding protein variations — which can otherwise distort total T4 — and provides the most reliable assessment of active hormone.
This test is part of standard thyroid evaluation, especially in pregnancy, liver or kidney disease, or any setting where binding proteins may be abnormal. It is also used to monitor patients on thyroid hormone replacement and to investigate central (pituitary) thyroid disorders, where TSH may not reflect actual thyroid hormone availability. Sample type is serum.
We are CLIA certified, the highest level of Medical industry compliance and standards.
Book an appointment