Home Tests Triiodothyronine - Free (FT3)

Triiodothyronine - Free (FT3)

This test measures the level of triiodothyronine (FT3) in your blood. FT3 is one of two major hormones made by your thyroid, a small, butterfly-shaped gland located near the throat. The other hormone is called thyroxine (T4.) T3 and T4 work together to regulate how your body uses energy. These hormones also play an important role in controlling your weight, body temperature, muscle strength, and nervous system.