T4 Free (FT4)

T4 Free (FT4)

Test Code

866
84439
CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.
866
84439
CPT Code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.
Not offered in Quest Diagnostics Nichols Institute (IFD) – San Juan Capistrano. Please provide SERVICE AREA INFORMATION to find available tests you can order.
In-home collection may be available in your area for purchase through Quest Mobile.

Clinical Significance

T4 Free (FT4) - The T4 Free (FT4) test measures serum thyroxine (T4) that is not bound to thyroid hormone-binding proteins (thyroid hormone-binding globulin [TBG], transthyretin, albumin) and is thus readily available to target cells. This test is used with thyroid-stimulating hormone measurement (TSH, test code 899) in the diagnosis of hyperthyroidism (usually displaying elevated FT4) and hypothyroidism (low FT4), including congenital and acquired hypothyroidism.

The FT4 test is used to assess thyroid function, monitor thyroid conditions, and assess treatment effectiveness. It has largely replaced the ...

Test Resources

Test FAQ

Hypogonadism

Test FAQ

T4, Free

Algorithm

Testing Algorithm for Thyroid Dysfunction in Nonpregnant Adults

Clinical Focus

Hypogonadism and Low Testosterone in Men: Laboratory Support of Diagnosis and Management

Clinical Focus

Thyroid Dysfunction in Nonpregnant Adults

Test Details

Methodology

Immunoassay (IA)

Reference Range(s)

<1 Month Not established
1-23 Months 0.9-1.4 ng/dL
2-12 Years 0.9-1.4 ng/dL
13-20 Years 0.8-1.4 ng/dL
>20 Years 0.8-1.8 ng/dL

Alternative Name(s)

FT4

LOINC® Codes, Performing Laboratory

Service Area must be determined

Methodology

Immunoassay (IA)

Reference Range(s)

<1 Month Not established
1-23 Months 0.9-1.4 ng/dL
2-12 Years 0.9-1.4 ng/dL
13-20 Years 0.8-1.4 ng/dL
>20 Years 0.8-1.8 ng/dL

Alternative Name(s)

FT4
Service Area must be determined

Preferred Specimen(s)

1 mL serum

Minimum Volume

0.3 mL

Transport Container

Serum separator tube (SST)

Transport Temperature

Room temperature

Specimen Stability

  • Room temperature: 7 days
  • Refrigerated: 7 days
  • Frozen: 28 days

Setup Schedule

Service Area must be determined
1 mL serum
0.3 mL
Serum separator tube (SST)
Room temperature
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Service Area must be determined
Not offered in Quest Diagnostics Nichols Institute (IFD) – San Juan Capistrano. Please provide SERVICE AREA INFORMATION to find available tests you can order.
In-home collection may be available in your area for purchase through Quest Mobile.
Test Details

Clinical Significance

Test Resources

Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

The CPT codes provided are based on AMA guidance and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

This material contains content from LOINC® (http://loinc.org). The LOINC Table, LOINC Table Core are copyright © 1995-2019, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and is available at no cost under the license at http://loinc.org/license.

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