Diagnostic Blood Test:

Thyroxine (T4), Total

Thyroxine or T4 is an inactive thyroid hormone produced by the thyroid gland. The liver and other tissues convert T4 into the active T3 thyroid hormone, which drives metabolism. Measuring T4 levels can help detect thyroid problems that can lead to changes in weight, mood, or heart rate.

Note: This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin. Cease biotin supplementation at least 72 hours prior to blood draw.