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T4, Free (Free Thyroxine)

Mnemonic:    [FT4]
Name:    T4, Free (Free Thyroxine)
Specimen:    1 mL serum from a Red SST or Red top tube.
Spec Stability:    Stable 5 days refrigerated.
Reference Range:    0.7 - 1.9 ng/dL
  Method:    Chemiluminescent Immunoassay
Note:    If the provider's order did not specify the type of T4 testing, order a Free T4.