TFT stands for Thyroid Function Test, which is a series of blood tests used to measure how well the thyroid gland is working. The most common TFTs are the TSH (Thyroid Stimulating Hormone) test and the T4 (thyroxine) test. The TSH test is often done first because it is the best way to initially test thyroid function. It determines whether a person has hyperthyroidism or hypothyroidism. The T4 test measures the amount of thyroxine in the blood, and a high level of T4 indicates an overactive thyroid (hyperthyroidism) . Other TFTs include the Free T4 test, which measures the amount of unbound thyroxine in the blood, and the Total T3 test, which measures the active form of the hormone. TFTs are used for diagnosis and to monitor treatment of common thyroid gland disorders. Despite their widespread use and high clinical efficacy, there is still considerable debate as to the optimum testing strategy for both the diagnosis and monitoring of thyroid dysfunction.