Free T3 (Triiodothyronine) Blood Test
The Free T3 Test measures the unbound, biologically active thyroid hormone T3. Although only a small fraction of T3 is free, it plays central roles in energy production, metabolism, cholesterol regulation, growth, and brain function. Free T3 is often reviewed with TSH and Free T4 for a complete thyroid picture.
Why Measure Free T3?
- Thyroid symptom workup: Clarify hyperthyroid patterns and treatment monitoring.
- Conversion context: Complements Free T4 to understand peripheral T4→T3 conversion.
Preparation & Notes
High-dose biotin can interfere with some immunoassays—only pause if your clinician advises.
How the PlexusDx Test Works
- At-home finger-prick;
- prepaid return mailer;
- results in ~2 business days;
- direct order; HSA/FSA accepted.
FAQ
Normal T3 but symptoms? Review TSH/Free T4, iron status, medications, and overall clinical context with your provider.
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