Thyroxine, Free (Free T4)
0070138
Ordering Recommendation
Not the preferred initial thyroid disorder screening test. Order following an abnormal thyroid stimulating hormone (TSH) result to diagnose thyroid disease. Order in conjunction with TSH in cases of suspected secondary hypothyroidism.
Mnemonic
FT4
Methodology
Quantitative Electrochemiluminescent Immunoassay
Performed
Sun-Sat
Reported
Within 24 hours  
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
Specimen Required
Patient Preparation
  
Collect
Serum separator tube or plasma separator tube. Also acceptable: Green (sodium or lithium heparin) or lavender (EDTA).  
Specimen Preparation
Allow specimen to clot completely at room temperature. Separate serum or plasma from cells ASAP or within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.5 mL)  
Storage/Transport Temperature
Refrigerated.  
Unacceptable Conditions
Grossly hemolyzed specimens.  
Remarks
  
Stability
After separation of cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 1 month  
Reference Interval
Effective May 16, 2011
 
Free Thyroxine, ng/dL
0-​3 days 0.7-​2.7 ng/dL
4-​30 days 0.8-​3.1 ng/dL
1-​23 months 0.5-​2.3 ng/dL
2-​6 years 0.9-​1.8 ng/dL
7-​11 years 0.9-​1.7 ng/dL
12-​19 years 0.9-​1.6 ng/dL
20 years and older 0.8-​1.7 ng/dL
Pregnancy, 1st Trimester 0.9-​1.4 ng/dL
Pregnancy, 2nd Trimester 0.7-​1.3 ng/dL
Interpretive Data
 
Note
 
CPT Code(s)
84439
Components
Component Test Code*Component Chart NameLOINC
0070138Thyroxine Free3024-7
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Free Thyroxine
  • FT4, Serum
  • Non-Protein Bound Tetraiodothyronine
  • T4 Free, Serum
  • T4, Free
  • Thyroid Function Cascade