Test ID FRT4D T4 (Thyroxine), Free, Dialysis, Serum
Useful For
Determining thyroid status of sick, hospitalized patients
Determining thyroid status of patients in whom abnormal binding proteins have been identified
Possibly useful in pediatric patients
Method Name
Equilibrium Dialysis/Tandem Mass Spectrometry (MS/MS)
Reporting Name
T4 (Thyroxine), Free by Dialysis, SSpecimen Type
SerumOrdering Guidance
The routine free thyroxine test (FRT4 / T4 [Thyroxine], Free, Serum) is faster and provides useful information in most patients.
Necessary Information
Include name and telephone number of contact physician.
Specimen Required
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 2.6 mL
Collection Instructions:
1. Draw blood immediately before next scheduled dose.
2. Centrifuge and aliquot serum into plastic vial within 2 hours of draw.
Specimen Minimum Volume
1.2 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 28 days | |
Frozen | 21 days | ||
Ambient | 7 days |
Reference Values
0.8-2.0 ng/dL
Reference values apply to all ages.
Day(s) Performed
Monday, Wednesday, Thursday
Performing Laboratory

CPT Code Information
84439
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
FRT4D | T4 (Thyroxine), Free by Dialysis, S | 6892-4 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
8859 | T4 (Thyroxine), Free by Dialysis, S | 6892-4 |