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HelpTest ID FRT3 T3 (Triiodothyronine), Free, Serum
Specimen Required
Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.6 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial.
Useful For
Free T3 (triiodothyronine) is a second- or third-level test of thyroid function; it provides further confirmation of hyperthyroidism, supplementing the T4 (tetraiodothyronine), sensitive thyrotropin, 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, SSpecimen Type
SerumSpecimen 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
For SI unit Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Day(s) Performed
Monday through Saturday
Report Available
1 to 3 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US 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.CPT Code Information
84481
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FRT3 | T3 (Triiodothyronine), Free, S | 83127-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| FRT3C | T3 (Triiodothyronine), Free, S | 83127-1 |