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Test ID FRT3 T3 (Triiodothyronine), Free, Serum

Useful For

Free triiodothyronine (T3) is a second- or third-level test of thyroid function; it provides further confirmation of hyperthyroidism, supplementing the tetraiodothyronine (T4), sensitive thyrotropin (sTSH), and total T3 assays

 

Evaluating clinically euthyroid patients who have an altered distribution of binding proteins

 

Monitoring thyroid hormone replacement therapy

Method Name

Immunoenzymatic Assay

Reporting Name

T3 (Triiodothyronine), Free, S

Specimen Type

Serum

Specimen Required

Container/Tube: 

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

Additional Information: Twelve hours before this blood test, do not take multivitamins or dietary supplements containing biotin or vitamin B7 that are commonly found in hair, skin and nail supplements and multivitamins.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  90 days

Reference Values

≥1 year: 2.8-4.4 pg/mL

Day(s) and Time(s) Performed

Monday through Friday; 5 a.m.-12 a.m.

Saturday; 6 a.m.-6 p.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

CPT Code Information

84481

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FRT3 T3 (Triiodothyronine), Free, S 3051-0

 

Result ID Test Result Name Result LOINC Value
FRT3C T3 (Triiodothyronine), Free, S 3051-0

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.