The Total T3 blood test measures the levels of triiodothyronine (T3) hormone in the bloodstream. T3 is one of the two primary hormones produced by the thyroid gland, and it plays a crucial role in regulating metabolism, growth, and development in the body.

The Total T3 blood test measures the total amount of T3 in the bloodstream, which includes both bound (attached to proteins) and unbound (free) T3. The test is often ordered as part of a thyroid function panel to help diagnose and monitor thyroid disorders, including hyperthyroidism (an overactive thyroid) and hypothyroidism (an underactive thyroid).

The normal range for Total T3 levels can vary depending on factors such as age, gender, and the laboratory performing the test. Generally, normal total T3 levels range from 80 to 200 ng/dL. Low total T3 levels may indicate hypothyroidism, while high total T3 levels may indicate hyperthyroidism.

It is important to note that the Total T3 test is not the most sensitive indicator of thyroid function, as it measures both bound and unbound T3 levels. Free T3 (unbound T3) is considered a more accurate measure of thyroid function and may be ordered in conjunction with the Total T3 test for a more complete evaluation.