Sign in →

Test Code T3T T3, Total (Triiodothyronine)

Important Note

Human Anti-Mouse Antibodies (HAMA) may be present in samples from patients who have received immunotherapy utilizing monoclonal antibodies. Additionally, other heterophile antibodies such as human anti-goat antibodies may be present in patient samples. Manufacturers formulate assays to minimize the effects of these antibodies; however careful evaluation of patient results must be done when patients are known to have such antibodies.

Access Total T3: potential of falsely elevated results when biotin concentrations are > 1 ng/mL.

Additional Codes

Powerchart: T3, Total
MA Cerner: T3 Total

Specimen Requirement

1.0 mL Serum or heparin plasma.

Additional Specimen Collection Information

Collection Instructions:
• Minimum volume: 500 mcL serum or heparin plasma
• Hemolysis: does not interfere with this assay
• Lipemia: does not interfere with this assay
• Icterus: No significant interference noted at 10 mg/dL.
• Storage: Store at room temperature for up to 8 hours. If specimens are stored longer than 8 hours keep refrigerated (2-8C) until transport to the lab.

Reference Value

0.9-1.8 ng/mL


Testing is performed Monday through Sunday.
Routine: Typically completed within 4 hours after the specimen arrives at the testing site.
STAT: Typically completed within 1 hour after the specimen arrives at the testing site.

CPT Code Information


Test Method

Two-Site Immunoassay; Beckman

Useful For

The clinical importance of Total T3 determination is in the diagnosis of thyroid disorders. Elevated concentrations of T3 can be found in Grave’s disease, and most other classical causes of hyperthyroidism. Decreased concentrations occur in primary hypothyroid diseases such as Hashimoto’s thyroiditis and neonatal hypothyroidism or secondary hypothyroidism due to defects at the hypothalamo-hypophyseal level.