T4 (Thyroxine), Total

Test Code

CPT Codes

Preferred Specimen
1 mL serum

Minimum Volume
0.5 mL

Other Acceptable Specimens
Plasma collected in a sodium or lithium (green-top) tube

Transport Container
Plastic screw-cap vial

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Immunoassay (IA)

Setup Schedule
Set up: Daily; Report available: Next day

Nonthyroidal chronic diseases, nicotinic acid and nutrition may decrease results. Thyrotoxicosis may not always cause abnormal results. Binding protein variations may cause variations in results. Increases may be associated with pregnancy or oral contraceptive use.

Reference Range
T4 (Thyroxine), Total
  Male (mcg/dL) Female (mcg/dL)
<1 Month 4.5-17.2 4.5-17.2
1-23 Months 5.9-13.9 5.9-13.9
2-12 Years 5.7-11.6 5.7-11.6
13-20 Years 5.1-10.3 5.3-11.7
>20 Years 4.9-10.5 5.1-11.9

Free T4 Index (T7) 1.4-3.8

Clinical Significance
For diagnosis of hypothyroidism and hyperthyroidism.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.