Ordering Recommendation

Not recommended for routine evaluation of thyroid disorders. Preferred test is Thyroxine, Free (Free FT4) (0070138).


Quantitative Equilibrium Dialysis/High Performance Liquid Chromatography-Tandem Mass Spectrometry


Sun, Tue, Thu


2-5 days

New York DOH Approval Status

This test is New York DOH approved.

Specimen Required

Patient Preparation

Plain Red or Serum Separator Tube (SST).

Specimen Preparation

Separate from cells or gel ASAP or within 2 hours of collection.  Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 mL)

Storage/Transport Temperature


Unacceptable Conditions



After separation from cells: Ambient: 4 days; Refrigerated: 2 weeks; Frozen: 1 month

Reference Interval

Effective May 16, 2011

Free Thyroxine ng/dL
Age Female Male
25-30 weeks gestation 0.5-3.3 ng/dL 0.5-3.3 ng/dL
31-36 weeks gestation 1.3-4.7 ng/dL 1.3-4.7 ng/dL
Birth to 1 week 2.2-5.3 ng/dL 2.2-5.3 ng/dL
2-3 weeks 0.9-4.0 ng/dL 0.9-4.0 ng/dL
1-5 months 1.1-2.2 ng/dL 1.1-2.2 ng/dL
6 months-6 years 1.4-2.7 ng/dL 1.4-2.7 ng/dL
7 years-17 years 1.1-2.0 ng/dL 1.1-2.0 ng/dL
18 years and older 1.1-2.4 ng/dL 1.1-2.4 ng/dL
Pregnancy, 1st Trimester 0.7-2.0 ng/dL
Pregnancy, 2nd Trimester 0.7-2.1 ng/dL
Pregnancy, 3rd Trimester 0.5-1.6 ng/dL

Interpretive Data

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
0093244 Free T4 by Equil Dialysis-TMS 6892-4
* 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.


  • Direct Dialysis
  • FT4
  • T4, Free, Equilibrium Dialysis
Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry