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Boston Heart Free T4 Test

Boston HeartSKU: AFH-1016-I4-ICD
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Free T4 is the amount of T4 hormone that is freely circulating in the blood.
Full Description

Free T4 (Free Thyroxine or FT4)

Free T4 is the amount of T4 hormone that is freely circulating in the blood.

Methodology

Chemiluminescence immunoassay

Patient Preparation

None

Preferred Specimen

1.0 mL serum collected in a serum separator tube (SST / Tiger Top)

Alternate Specimen

1.0 mL plasma in an EDTA plasma separator tube (Pearl Top)

Transport Temperature

Refrigerated (ship on frozen cold packs)

Stability

Refrigerated: 7 days  (7 days on SST gel)

 

  • Low: <0.93 ng/dL
  • Optimal: 0.93-1.70 ng/dL
  • High: >1.70 ng/dL

 

Low Free T4 levels are consistent with an underactive thyroid gland or inadequate thyroid hormone replacement.1-3

High Free T4 levels are consistent with either an overactive thyroid gland or excess thyroid hormone replacement.1-3

High doses of biotin (> 5 mg/day) may interfere with assay results. Patient assumed to be refraining from biotin supplementation for at least 3 days prior to blood draw.

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