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Test Code Billings Clinic: 4033 T3 (Triiodothyronine), Uptake, Plasma or Serum

Important Note

This test is included in Billings Clinic: #4035 “Thyroid Panel” and is not usually ordered individually.

Performing Laboratory

Billings Clinic Laboratory: Chemistry

Useful For

  • Assessment of thyroid function status


Chemiluminescent Immunoassay


Specimen Requirements

Submit only 1 of the following specimens:

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.



  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 1.0 mL of heparinized plasma frozen.



  • Draw blood in a plain, red-top tube(s) or a serum gel tube(s).
  • Spin down and send 1.0 mL of serum frozen


Specimen Type Temperature Time
Plasma, Serum Refrigerated 2 days
  Frozen (preferred) 1 month
  Ambient 8 hours


Reject Due To

  • Specimens with apparent contamination
  • Specimens stored at room temperature greater than 8 hours
  • Samples frozen and thawed more than once

Reference Values

Males:  33 - 40 %

Females:  30 - 39 %

Day(s) Test Set Up


Test Classification and CPT Coding

84479 - Thyroid hormone (T3) uptake

LCD or NCD test. ICD-10 code is required for this test. When appropriate, obtain a properly executed ABN and submit the ABN with test order(s). See “Medical Necessity and Advanced Beneficiary Notice (ABN) Policy and Form” under Resources for a copy of a form and additional information.

LOINC Code Information

Reporting Name LOINC Code
T3 Uptake 32215-6