T3 Free


For: ,

Quest Diagnostics Test Code: 34429

This test is used to diagnose hyperthyroidism and to clarify thyroid status in the presence of a possible protein binding abnormality.

T3, also known as triiodothyronine, is a hormone that is released from the thyroid gland. Together with the hormone T4, they help to regulate body metabolism and energy expenditure rate. T3 is released into the bloodstream from the thyroid gland and travels to its target organs while being bound to plasma proteins. When T3 is bound to plasma proteins, it is in its inactive form. If it is not bound, it is referred to as free T3, and this is the active hormone which can exert its effect. The total measurement of T3 in the blood is measured by the amount of free T3 plus bound T3. This test is performed as a marker of thyroid function, for disease like hyper and hypothyroidism.

This test is performed in following conditions such as:

Signs and symptoms of hyperthyroidism
• Weight loss
• Increased heart rate
• Anxiety
• Difficulty sleeping
Signs and symptoms of hypothyroidism
• Weight gain
• Dry skin
• Constipation
• Cold intolerance

Also Known As: Free T3, Triiodothyronine


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround time for a Free T3 test is typically 1 business day.