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Test ID T4 T4 (Thyroxine), Total Only, Serum

Useful For

Monitoring treatment with synthetic hormones (synthetic triiodothyronine will cause a low total thyroxine: T4)

 

Monitoring treatment of hyperthyroidism with thiouracil and other antithyroid drugs

 

Total T4 levels offer a good index of thyroid function when the thyroid-binding globulin is normal and nonthyroidal illness is not present

Method Name

Electrochemiluminescence Immunoassay

Reporting Name

T4 (Thyroxine), Total Only, S

Specimen Type

Serum

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Additional Information: 12 hours before this blood test do not take multivitamins or dietary supplements containing biotin or vitamin B7, which are commonly found in hair, skin, and nail supplements and multivitamins.

Forms: If not ordering electronically, complete, print, and send a Neurology Test Request Form-General (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

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

Reference Values

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

Day(s) and Time(s) Performed

Monday through Friday 5 a.m. – 12 a.m., Saturday 6 a.m. – 6 p.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

CPT Code Information

84436

LOINC Code Information

Test ID Test Order Name Order LOINC Value
T4 T4 (Thyroxine), Total Only, S 3026-2

 

Result ID Test Result Name Result LOINC Value
T4 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.

Testing Algorithm

See Thyroid Function Ordering Algorithm in Special Instructions.