Synonyms: Free T4, Direct, Serum; Free Thyroxine; T4, Free, Direct; T4, Free, Direct, Serum; Unbound T4

(Note: necessary lab analysis process requires 5-8 days to receive results)

Why It Is Done

This test is used to evaluate thyroid function and screen for hyperthyroidism or hypothyroidism.

Test Overview

Free thyroxine index (FTI or FT4). Free thyroxine (T4) can be measured directly (FT4) or calculated as the free thyroxine index (FTI). The FTI tells how much T4 is present compared to the thyroxine-binding globulin. The FTI can help tell if abnormal amounts of T4 are present because of abnormal amounts of thyroxin-binding globulin.

How To Prepare

No special preparation required