Blood Test Types
The free T4 are tests thelps evaluate thyroid function. The free T4 test is used to help diagnose hyperthyroidism and hypothyroidism. Free T4 is the active form of thyroxine and is usually ordered along with or following a TSH test. This helps the doctor to determine whether the thyroid hormone feedback system is functioning as it should, and the results of the tests help to distinguish between different causes of hyperthyroidism and hypothyroidism.