Free T4

Test Code

T4F

CPT Codes
84439

Preferred Specimen

Serum Separator (Gold/Yellow) Tube

Patient Preparation
Patient must avoid Biotin consumption prior to collection.

Minimum Volume

0.5 mL

Other Acceptable Specimens

Lithium Heparin Plasma Separator (Light Green) Tube

Transport Temperature

Refrigerated

Specimen Stability

MercyOne Dakota Dunes Medical Laboratory
Room Temperature: 24 hrs - Serum and Plasma
Refrigerated: 5 days - Serum Only
Frozen: 7 days - Serum and Plasma

MercyOne Siouxland Medical Laboratory
Room Temperature: 24 hrs - Serum and Plasma
Refrigerated: 2 days - Plasma only
Frozen: 7 days - Serum and Plasma

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Hemolysis, Icterus, Lipemia

Reference Range

Age		Reference Low	Reference High
0 Minutes	2 Years	0.88	1.48
2 Years	13 Years	0.81	1.35
13 Years	21 Years	0.78	1.33
21 Years	150 Years	0.75	1.4

Performing Laboratory
This test is performed at the following locations:

MercyOne Siouxland Medical Laboratory
MercyOne Dakota Dunes Medical Laboratory

Last Updated: March 11, 2025

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.