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

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


EMIT / bichromatic rate


Specimen Requirements

  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 1 mL of heparinized plasma frozen in plastic vial.


Specimen Type Temperature Time
Plasma Refrigerated 2 days
  Frozen (preferred) 3 months


Reject Due To

  • Avoid repeated freezing and thawing

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 3023-9