Test Overview
Test Methodology

Chemiluminescent Immunoassay

Test Usage

Thyroid function test, particularly useful in the diagnosis of T3 thyrotoxicosis and confirmation of hyperthyroidism. Needed in patients with clinical evidence for hyperthyroidism, in whom thyroid profile is normal or borderline.

Reference Range *

80 - 175 ng/dL

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

Specimen may be stored at room temperature up to 8 hours. [12/05]

Influenced by state of nutrition and alterations in liver function due to TBG production. Serum T3 levels are increased during pregnancy and in women receiving oral contraceptives. Levels decreased by acute and chronic illness and by some drugs.

Test Details
Days Set Up
Daily, 24 hours
Analytic Time

4 hours

Soft Order Code
MiChart Code
  • Synthroid (Levothyroxine)
  • Triiodothyronine
  • T3
  • T3 TOTAL
Chemical Pathology
Specimen Requirements
Collection Instructions

Collect specimen in a red top or SST tube. Centrifuge, aliquot serum into a plastic vial and refrigerate up to 48 hours or freeze for longer storage.

Alternate Specimen
Red Top Tube
Normal Volume
0.5 mL serum
Minimum Volume
0.25 mL serum
Rejection Criteria
Anticoagulants not acceptable.
Additional Information

Hyperproduction of T3 always occurs in hyperthyroidism. In addition, in approximately 5% of hyperthyroidism only T3 (and not T4) is elevated. This occurs in early hyperthyroid states and in hyperthyroid individuals in iodine deficient areas. Reduced levels of T3 are associated with compromised liver function, malnutrition and possibly with advancing age.

CPT Code
Fee Code