T3, Free

Test performed at York Hospital Laboratory.

Test Code

Alias/See Also
Free T3

CPT Codes

Preferred Specimen
0.2 mL serum collected in a serum separator tube (SST)

Other Acceptable Specimens
0.2 mL serum collected in a no additive (red-top) tube, transferred to a plastic screw-cap vial 0.2 mL plasma collected in a lithium heparin (green-top) gel separator tube

Transport Temperature

Specimen Stability
Room temperature: 4 hours
Refrigerated: 7 days
Frozen: 4 weeks


Setup Schedule

Report Available
Next Day

Reference Range
2.77-5.27 pg/mL

Clinical Significance
  • In hyperthyroidism, FT3 concentrations are generally elevated and give efficient discrimination at the euthyroid/toxic borderline, providing an effective method for confirming hyperthyroidism and monitoring of its treatment. In hypothyroidism, FT3 concentrations tend to be lower, but the decrease is insufficient to give clear diagnostic information. FT3 concentrations are independent of the concentration of thyroid hormone binding proteins, and may be measured in patients with elevated or reduced binding protein concentrations without the need for additional tests of binding capacity.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.