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Test Code 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.

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

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

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.

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

Method Name

Electrochemiluminescence Immunoassay