Thyroxine T4 (Total)

Tube Type = Mint Green Top

Tube Type

Test ID LAB126
EPIC Order
 T4 TOTAL
CPT Code(s) 84436
Group/Individual Test Individual
Laboratory Core Laboratory
Tube Station 30
Specimen Routine: 4 mL blood/gold SST tube. Also acceptable orange, or red plain tube; 
See Comments
Micro: 2 micro collection devices/900 µL blood gold top/ red top/ or orange top
Stability
Unspun: 8 hours
Spun/separated, Room Temp-<8 hrs recommended
Spun/separated, Refrigerator: 48 hours
Spun/separated, Frozen: 30 days
Availability Routine: 24 hrs/day
Turnaround Time 2 hrs
Reference Range
Age T4 Reference Range (ug/dL)
0-1 month Undefined
1-23 months 6.00-13.20
23 months-12 years 5.50-12.10
12-20 years 5.50-11.10
+20 years 4.50-10.90
Comments
  • Please do not order in addition to Free T4
  • Light green lithium heparin plasma is not an acceptable specimen type
  • Reference Range effective 7-13-2021
  • Testing is performed using the Siemens Atellica T4 Assay. Heterophilic antibodies may cause interference.
  • Phenytoin may interfere with T4 measurement due to competition for TBG binding sites.

Reviewed by J. Carr on January 02, 2026

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