Use

A Total T3 (triiodothyronine) test is a crucial tool in hormone management and health optimization, providing insights into thyroid function and metabolism. While TSH and Free T4 are commonly measured, Total T3 offers a more comprehensive view of thyroid activity, as it represents both bound and free T3 in circulation. Since T3 is the most biologically active thyroid hormone, assessing its levels helps determine how effectively the body is converting T4 into its active form, which is essential for regulating energy, metabolism, mood, and overall physiological balance.

For individuals undergoing hormone optimization therapy, Total T3 testing is particularly useful in diagnosing and managing conditions such as hypothyroidism, hyperthyroidism, or suboptimal thyroid function that may not be apparent through TSH alone. Patients with persistent fatigue, weight fluctuations, brain fog, or difficulty maintaining body temperature can benefit from a deeper thyroid assessment, ensuring that treatment plans—whether through lifestyle changes, medication, or hormone therapy—are truly optimizing thyroid function. By monitoring Total T3 levels, healthcare providers can make more precise adjustments to thyroid hormone therapy, ensuring that patients achieve optimal metabolic and endocrine balance for long-term health and vitality.

Thyroid function which is particularly useful in the diagnosis of T₃ thyrotoxicosis, in which T₃ is increased and T₄ is within normal limits. T₃ toxicosis is occasionally found in Graves’ disease. It occurs with a single toxic nodule, multinodular thyrotoxicosis, and following treatment with T₃ (Cytomel®). It is increased in and occasionally helpful for confirmation of diagnosis of conventional hyperthyroidism, in which commonly both T₃ and T₄ levels are increased. T₃ is needed in patients with clinical evidence for hyperthyroidism, in whom the usual thyroid profile is normal or borderline.

Recommended for patients with supraventricular tachycardia, for patients with fatigue and weight loss not otherwise explained, or for those with proximal myopathy and in whom T₄ levels are not elevated.

Preparation 

Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.