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Mayo Clinic Laboratories

Test Code FT4 T4 (Thyroxine), Free

Additional Codes

Compendium Code (Iatric): 303.1049

Performing Laboratory

St. Lukes Hospital Laboratory

Methodology

Competitive Chemiluminescent Immunoassay

Specimen Requirements

Do not use samples that have been stored at room temperature for longer than 8 hours.

Tightly cap and refrigerate specimens at 2–8°up to 48 hours.

Draw blood in a serum gel tube(s) preferred. Plasma from lithium heparin is acceptable. 

Spin down and send 1 mL of serum (or plasma) refrigerated.

 

Unspun specimens must be transported at ambient temperature and arrive to the laboratory within one hour of draw.

Reference Values

0.80-1.76 ng/dL

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

CPT: 84439

LOINC: 3024-7