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Test ID T4FT4 T4 (Thyroxine), Total and Free

Useful For

Thyroxine (T4) and free T4 are measured together with thyroid-stimulating hormone when thyroid function disorders are suspected.

Method Name

Electrochemiluminescence Immunoassay

Reporting Name

T4 (Thyroxine), Total and Free

Specimen Type

Serum


Specimen Required


Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL


Specimen Minimum Volume

0.625 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  30 days
  Ambient  72 hours

Reference Values

T4 (THYROXINE), TOTAL ONLY

Adult (≥20 years): 4.5-11.7 mcg/dL

Pediatric:

0-5 days: 5.0-18.5 mcg/dL

6 days-2 months: 5.4-17.0 mcg/dL

3 -11 months: 5.7-16.0 mcg/dL

1 -5 years: 6.0-14.7 mcg/dL

6 -10 years: 6.0-13.8 mcg/dL

11 -19 years: 5.9-13.2 mcg/dL

 

T4 (THYROXINE), FREE

Adult (≥20 years of age): 0.9-1.7 ng/dL

0-5 days: 0.9-2.5 ng/dL

6 days-2 months: 0.9-2.2 ng/dL

3-11 months: 0.9-2.0 ng/dL

1-5 years: 1.0-1.8 ng/dL

6-10 years: 1.0-1.7 ng/dL

11-19 years: 1.0-1.6 ng/dL

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Performing Laboratory

Mayo Medical Laboratories in Rochester

CPT Code Information

84436-Total

84439-Free

LOINC Code Information

Result ID Test Result Name Result LOINC Value
T4F T4 (Thyroxine), Free, S 3024-7
T4CC T4 (Thyroxine), Total Only, S 3026-2

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

Profile Information

Test ID Reporting Name Available Separately Always Performed
T4F T4 (Thyroxine), Free, S No Yes
T4CC T4 (Thyroxine), Total Only, S No Yes