Alert

T4 Free

Free T4; Thyroxine, Free

Tube Type

Test ID
LAB127
EPIC Order
T4, FREE
CPT Code(s)
84439
Group/Individual Test
Individual
Laboratory
Core Laboratory
Tube Station
30; STAT: 888
Specimen
Routine:
4 mL blood/serum separator tube/gold top/red top acceptable
Micro:
0.9 mL blood/gold or red top bullet
Stability
Unspun: 8 hours
Spun/separated, Room Temperature-</=8 hrs recommended
Spun/separated, Refrigerator: 7 days
Spun/separated, Frozen: 4 weeks
Availability
Routine:
24 hrs/day
STAT:
Yes
Turnaround Time
Routine: 2 hrs; STAT: 1 hr
Reference Range
Normal:
See table below
Comments
For additional specimen information refer to Core Laboratory Memorandum #46
Thyroid hormone autoantibodies in serum samples may cause interference in free-hormone immunoassays. Heterophilic antibodies may cause test interference.
Free T4 Reference Ranges (ng/dL)
Pediatric patients¹
0-3 d
2.00-5.00
3-30 d
0.90-2.20
31 d - 18 y
0.80-2.00
Adults, ambulatory, healthy2
>18 y
0.71-1.40
Pregnant, euthyroid patients3
Levels trend 23-38% lower than the reference mean. The lowest point typically occurs ~34-36 w.
1. Dugaw KA, Jack RM, Rutledge J Pediatric reference ranges for TSH, free T4, total T4, total T3, and T3 Uptake on the Vitros ECi analyzer. Clin Chem 2001; 47: A108.
2. Reference range determined in-house
3. Lockitch G. Handbook of Diagnostic Biochemistry and Hematology in Normal Pregnancy. CRC Press. 1993.

Reviewed by Christopher Parker on December 16, 2019

Note: Reference ranges provided on this web site are for guidance only, and may not reflect the most recent changes. Refer to laboratory reports for current reference data.

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