Total T4 (Thyroxine, Total)

CPT: 84436
Thyroid

What This Test Measures

Measures total thyroxine (bound + free) in blood; less specific than Free T4 due to protein binding effects.

Preparation

No fasting required
If taking T3 medication (liothyronine/Cytomel), draw at least 12–24 hours after your last dose for an accurate TSH. If splitting T3 doses, draw at your natural trough. Biotin supplements — even in multivitamins — can falsely skew thyroid results: discontinue at least 2 days before testing. No fasting required unless combined with other tests.

General guidelines only. Requirements vary by lab and individual. Confirm with your provider before adjusting any medications.

Turnaround Time

Varies by lab

Clinical Notes

Affected by pregnancy, estrogen, liver disease; less preferred than Free T4

ICD-10 Codes

Common diagnosis codes associated with this test. Codes are assigned by your provider.

E03.9Hypothyroidism, unspecified
E05.90Hyperthyroidism, unspecified
R53.83Other fatigue

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Lab Codes

Proprietary codes used by each lab for this test.

ARUP Laboratories
0070140(order_code)
CPL
2819(order_code)
LabCorp
001149(order_code)
NYU Langone Health
LAB10296(order_code)
Quest Diagnostics
867(order_code)
Stanford Health Care
TES(order_code)

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Related Tests

Free T4 (Thyroxine, Free)

CPT: 84439

Free T3 (Triiodothyronine, Free)

CPT: 84481

Free T4 Index (T7)

CPT: 84479, 84436

Anti-TPO (Thyroid Peroxidase Antibody)

CPT: 86376

Anti-Thyroglobulin Antibody (TgAb)

CPT: 86800

Comprehensive Thyroid Panel

CPT: 84443, 84439, 84481, 84482, 86376, 86800

For informational purposes only

This page is for educational and research purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. ICD-10 and CPT codes are assigned by your healthcare provider. Always consult a qualified healthcare provider before ordering any lab test or making decisions about your health.