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Free T3 Unit Converter
Free Triiodothyronine (FT3) is the unbound, biologically active form of T3. It represents only about 0.3% of the total T3 in the blood but is responsible for most of the metabolic effects of thyroid hormone.
FT3 measurements are particularly useful in diagnosing **T3 toxicosis** (hyperthyroidism with normal T4) and monitoring response to antithyroid treatment. This converter facilitates switching between standard mass units (pg/mL) and SI molar units (pmol/L).
Mass Units (US)
StandardPicograms per milliliter (Most common for Free T3).
SI Units / Molar
Picomoles per liter (International Standard).
Clinical Context
Reference Ranges (Adults):
• Conventional: 2.0 – 4.4 pg/mL (0.2 – 0.44 ng/dL).
• SI: 3.1 – 6.8 pmol/L.
Interpretation:
• High FT3: Hyperthyroidism, Graves’ disease, toxic nodular goiter.
• Low FT3: Hypothyroidism, or Non-thyroidal illness (“Low T3 syndrome”). Note: FT3 is often the last test to become abnormal in hypothyroidism.
Conversion Logic:
Molecular Weight of T3: ~650.97 g/mol.
1 pg/mL ≈ 1.536 pmol/L.
1 pmol/L ≈ 0.651 pg/mL.
Clinical References
How to Use This Converter
Follow these steps to normalize FT3 values.
Enter Values
Input your laboratory result into the corresponding unit field (e.g., pg/mL).
Automatic Conversion
The calculator converts between mass units and the SI molar unit using the molecular weight of 650.97 g/mol.
Reset
Use the Clear button to reset all fields.
Frequently Asked Questions
Yes. 1 picogram per milliliter (pg/mL) is numerically identical to 1 nanogram per liter (ng/L).
Total T3 is affected by protein levels (like TBG). FT3 measures the unbound, active hormone, making it a better indicator of true thyroid status in conditions like pregnancy.