T4 (Thyroxine), Free, Plasma or Serum

Test Code

Free T4/FT4 - NOCO

CPT Codes
84439

Preferred Specimen

1 mL plasma from Green top (Lithium Heparin)

Minimum Volume

0.5 mL

Other Acceptable Specimens

1.0 mL serum from SST or Red Top

Specimen Stability

Specimen Type	Temperature	Time
Serum SST	Refrigerated	7 days
Red Top – Separated*	Refrigerated	7 days
Plasma Li Hep	Refrigerated	7 days

*Centrifuge and aliquot into a plastic vial.

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

Gross hemolysis, Collection after IV contrast material

Methodology

Setup Schedule

Monday through Sunday; Continuously

Report Available

Same day

Reference Range

Refer to the Chemistry Reference Range and Critical Results documents in the Resources file on the facility test directory page.

Performing Laboratory
Banner Fort Collins Medical Center Laboratory
North Colorado Medical Center Laboratory

Last Updated: August 13, 2026

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.