Sign in →

Test ID T3 T3 (Triiodothyronine), Total, Serum

Useful For

Second-order testing for hyperthyroidism in patients with low thyroid stimulating hormone values and normal T4 levels


Diagnosis of T3 toxicosis

Testing Algorithm

See Thyroid Function Ordering Algorithm in Special Instructions.

Method Name

Immunoenzymatic Assay

Reporting Name

T3 (Triiodothyronine), Total, S

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

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: 80-190 ng/dL

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

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.

CPT Code Information


LOINC Code Information

Result ID Reporting Name LOINC Code
T3 T3 (Triiodothyronine), Total, S 3053-6