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Free Thyroxine (087-0703)
Test Mnemonic:


Specimen Requirements:

Routine venipuncture

AM collection preferred.  Collect 7mL of blood in SST (gel barrier) or 7 mL red-topped tube (see storage instructions). (Min.: 3mL of blood).

Minimum Volume:

3 mL of blood


Deliver to Sample Management within 2 hours of collection.

Specimen Preparation:

Allow specimen to clot completely at room temperature. Centrifuge to separate serum from cells within 2 hours of collection. Transfer serum from collection tube to labeled plastic transport tube.



Refrigerated for ≤ 7 days    or frozen for ≤ 4 weeks.  

Causes for Rejection:

Incomplete and/or incorrect sample identification, improper storage/transport, and gross hemolysis and lipemia.                               

Reference Range:

By report (reports may vary based on instrumentation, patient age and sex)

Turnaround Time:

Routine: 8 hours ASAP: 4 hours




24 hours a day; 7 days a week


Clinical Chemistry

Patient Preparation :

AM collection preferred. 

CPT 4 Code:


When ordering tests for which Medicare or Medicaid reimbursement will be sought, physicians should only order tests that are medically necessary for the diagnosis or treatment of the patient. Components of the organ or disease panels may be ordered individually. The diagnostic information must substantiate all tests ordered and must be in the form of an ICD-10 code or its verbal equivalent.
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