T3 Free

Tube Type = Mint Green Top

Tube Type

Free T3

Test ID

LAB137
EPIC Order
 T3, FREE
CPT Code(s) 84481
Group/Individual Test Individual
Laboratory Core Laboratory
Tube Station 30
Specimen Routine: 4 mL blood/green lithium heparin gel tube. Also acceptable gold SST tube or red plain tube
Micro: 0.9 mL blood/mint green top bullet/gold top/red top
Stability
Unspun: 4 hours
Spun/separated, Room Temperature: <8 hrs recommended
Spun/separated, Refrigerator: 48 hours
Spun/separated, Frozen: 30 days
Availability Routine: 24 hrs/7 days
STAT: Yes
Turnaround Time 2 hrs
Reference Range and
Interpretation

  

Age Group (years)

Free T3

Reference Range (pg/mL)
(effective 7/31/2021)
0-1 month undefined
1-23 months 3.30-5.20
23 months-12 years 3.30-4.80
12-20 years 3.0-4.70
20 years + 2.30-4.20
Comments
  • Thyroid hormone autoantibodies in serum samples may cause interference in free-hormone immunoassays.  Heterophilic antibodies may cause test interference.
  • Testing is performed using Siemens Atellica FT3 Assay. Performance of this assay has not been established with neonatal specimens.

Reviewed by J. Carr on January 02, 2026

UNC Hospitals
McLendon Clinical Laboratories
101 Manning Drive
Chapel Hill, NC 27514