The Free Triiodothyronine (Free T3) test measures the level of a hormone called free triiodothyronine (free T3) in your blood. T3 is produced by your thyroid gland and helps control your metabolism. This test is used to help diagnose thyroid disorders such as hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid). It can also be used to monitor the effectiveness of treatment for thyroid disorders.

Free T3 (Free Triiodothyronine) is the active form of thyroid hormone that can directly enter and affect body tissues.

Key Characteristics: • Represents the biologically active thyroid hormone • Not bound to proteins • Moves freely through the bloodstream

Normal Range: • 130 to 450 picograms per deciliter (pg/dL) • 3.1 to 6.8 pmol/L • 0.2 to 0.5 ng/dL

Clinical Significance: • Helps diagnose thyroid disorders • Less reliable than Total T3 test • Typically ordered after abnormal TSH results

Important Details: • Comprises approximately 5% of total thyroid hormones • 80% of T3 is converted from T4 in liver and kidneys • Regulates metabolism, growth, and cellular function

The Free T3 test provides healthcare providers with insights into thyroid hormone activity and potential metabolic dysfunction.