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Test Code FRT3 T3 (Triiodothyronine) Free, Plasma or Serum

Performing Laboratory

Bronson Laboratory Services-Chemistry

Reference Values

2.57-4.43 pg/mL


Chemiluminescent Immunoassay

This test is recommended over total T3 because the free T3
represents the physiologically active hormone rather than the
quantity of carrier proteins.

Specimen Requirements & Patient Preparation

Patient Preparation: For 12 hours before this test do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.   Biotin can interfere with many immunoassay tests.

Submit only 1 of the following specimens:



Specimen Type: Serum
Container/Tube: Gold or Red

Specimen Volume: 5 mL

Specimen Minimum Volume: 1 mL



Specimen Type: Plasma
Container/Tube: Mint or Green
Specimen Volume: 5 mL

Specimen Minimum Volume: 1 mL

Specimen Transport Temperature


Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding


Specimen Stability

Refrigerated - 7 days

Frozen - 1 month