Free T3

Abbreviation

FT3

Preferred Specimen

Serum

Minimum Volume

0.5mL

Collection Instructions

Routine venipuncture

Transport Container

Draw tube or plastic pour off tube

Transport Temp

Frozen

Stability

  • 2-8 C for 24 hours
  • -20C up to 12 months

Methodology

CLIA (chemiluminescent immunoassay)

Reference Ranges

  • Normal range: 2.2-4.2 pg/mL

Clinical Significance

To identify patients with thyrotoxicosis whose T4 and FT4 concentrations are normal, while T3 is elevated. FT3 is useful to identify subclinical hyperthyroidism with suppressed TSH, and nnormal Ft4 and FT3 levels.