Test guide
Triiodothyronine (T3) Tests
A triiodothyronine (T3) test measures the level of T3 in a sample of your blood. It's used to help diagnose thyroid disease .
What it is for
A T3 test is used to help: T3 tests are usually ordered with blood tests that measure T4 and TSH (thyroid stimulating hormone) tests. Source: MedlinePlus, National Library of Medicine. Medical test information is public domain. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Limitations
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also known as
- thyroid function test
- total triiodothyronine, free triiodothyronine, FT3, TT3, radioimmunoassay FT3
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