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Free T3

FT3 Free Triiodothyronine
Serum (SST) pmol/L

About this test

The most metabolically active thyroid hormone. Most useful in diagnosing T3 thyrotoxicosis and monitoring replacement therapy.

Reference Ranges

Sex Age Range Notes
All ≥ 18 yrs 3.1 – 6.8 Adult

Clinical Interpretation

Low / Decreased
Low — severe illness (low T3 syndrome), hypothyroidism, malnutrition.
High / Increased
Elevated — T3 thyrotoxicosis (early Graves', toxic nodule), excess liothyronine (T3) therapy.

Related Tests

Free T4
Specimen
Serum (SST)
Reporting Unit
pmol/L
Category
⚗️ Endocrinology

⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.