The Total T3 test is a blood test that measures the total concentration of the thyroid hormone TriiodothyronineT3 circulating in your bloodstream. This total measurement includes both T3 that is bound to proteins (which makes up the majority) and the small fraction that is free (unbound) and biologically active.
Triiodothyronine (Total T3) is one of the two main hormones produced by the thyroid gland (Total T4or Thyroxine).