Test ID T3 T3 (Triiodothyronine), Total, Serum
Useful For
Second-order testing for hyperthyroidism in patients with low thyroid-stimulating hormone values and normal thyroxine levels
Diagnosis of triiodothyronine toxicosis
This test is not useful for general screening of the population without a clinical suspicion of hyperthyroidism.
Special Instructions
Method Name
Electrochemiluminescence Immunoassay
Reporting Name
T3 (Triiodothyronine), Total, SSpecimen Type
SerumSpecimen 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.
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Specimen Minimum Volume
0.75 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 7 days | |
Frozen | 30 days |
Reference Values
Pediatric
0-5 days: 73-288 ng/dL
6 days-2 months: 80-275 ng/dL
3-11 months: 86-265 ng/dL
1-5 years: 92-248 ng/dL
6-10 years: 93-231 ng/dL
11-19 years: 91-218 ng/dL
Adult (≥20 years): 80-200 ng/dL
For SI unit Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Day(s) Performed
Monday through Friday
Performing Laboratory

CPT Code Information
84480
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
T3 | T3 (Triiodothyronine), Total, S | 83124-8 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
T3 | T3 (Triiodothyronine), Total, S | 83124-8 |
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.Testing Algorithm
See Thyroid Function Ordering Algorithm in Special Instructions.