T3 Free Blood Test - More Information

The T3 free test, also known as a T3 free blood test and a free T3 lab test, measures the free T3 blood level.

T3, or triiodothyronine, is a hormone produced by the thyroid gland to help with metabolism. The "free" component of the T3 test represents triiodothyronine floating unbound to proteins in the blood. To get through the blood, most triiodothyronine is transported by a carrier protein while the free T3 (a small percentage of the total) floats freely. At the cellular level, free T3 is readily accessible by cells (i.e. bioavailable) while bound T3 takes longer to be absorbed because it first has to detach from the carrier protein. As a result, the free T3 blood level is often ordered in conjunction with the total T3 level to get a more complete picture of one's T3 hormone status.

To get a T3 free test near you, order online and get tested at Quest Diagnostics. Once the T3 free lab results are ready, they will be available for download. As can be seen on the sample T3 free lab report, the T3 free blood level is reported as a numerical value and can be compared against the reference range provided by the lab.

Some people are interested in the T3 free test as part of a more comprehensive evaluation for a more complex thyroid condition. As a result, the free T3 blood test is also part of specialized thyroid panels such as the Graves' disease test panel and the Hashimoto's test panel. The T3 free test is also tested in the hyperthyroidism test panel and as part of the thyroid comprehensive test panel.