Laboratory Lab results are too important to go anywhere else.

Free T4 (Thyroxine) by Equilibrium Dialysis

Test Codes

This test is only available to Endocrinologists and Nuclear Medicine Physicians.

Department

Send Outs

Instructions

This test is only available to Endocrinologists and Nuclear Medicine Physicians.

Specimen Collection Criteria

Collect (preferred specimen): One Gold-top SST tube.
Also acceptable: one Red top tube.

Physician Office/Draw Specimen Preparation

Centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Preparation for Courier Transport

Transport: 2.6 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 1.5 mL)

Rejection Criteria

Specimens not collected and processed as indicated.

In-Lab Processing

Centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Transport: 2.6 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 1.5 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 28 days
Frozen (-20°C/-4°F or below): 21 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Mayo Clinic Laboratories in Rochester, MN.

Performed

Monday, Wednesday, Thursday.
Results available in 4-9 days.

Reference Range

By Report.

Test Methodology

Equilibrium Dialysis/Tandem Mass Spectrometry (MS/MS)

Interpretation

By Report.

CPT Codes

84439

Contacts

Last Updated

9/19/2023