Biomarker Lens

Common biomarkers

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  • Ferritin
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  • Alkaline Phosphatase
  • FSH
  • T4,Free(Direct)

Biomarkers · Chemical

T4,Free(Direct)

Thyroxine is also called T4. T4 is a hormone that your thyroid gland makes.

Thyroxine (T4) Test, MedlinePlus, National Library of Medicine

Primary unit
ng/dL
LOINC codes
3024-7
Tests that measure T4,Free(Direct)
Labcorp 3, Quest Diagnostics 1

Ranges

Compare the reference ranges labs publish with guideline targets, diagnostic cut-offs, study-based ranges and practitioner targets. Move across the rows to check a value against each range, and open a source from the legend. How to read these ranges

T4,Free(Direct), ng/dL

Labs
  • Lab reference ranges2 labs
All 2 published ranges, with sources

Lab reference ranges

Tests

Check the catalog code, specimen, method and preparation for every test that measures T4,Free(Direct). Select up to five tests to compare them side by side.

Labcorp 3 tests

Single-analyte tests

  • Thyroxine (T4), Free, Direct 001974

    Serum · Fasting not stated · Turnaround Within 1 day

    Method and collection
    Method
    Electrochemiluminescence immunoassay (ECLIA) This assay is performed on the Roche cobas instrument in multiple laboratories throughout Labcorp.
    Preparation
    Heparin has been reported to have in vivo and in vitro effects on free T4 assay. Hence samples should not be collected during or soon after the administration of this anticoagulant.
    Collection
    If a red-top tube or plasma is used, transfer separated serum or plasma to a plastic transport tube.
    Reference notes
    See table.1 Age | Range (ng/dL) 0 to 3 d | 0.66−2.71 4 to 30 d | 0.83−3.09 31 d to 12 m | 0.48−2.34 13 m to 5 y | 0.85−1.75 6 to 10 y | 0.90−1.67 11 to 19 y | 0.93−1.60 >19 y | 0.82−1.77
    Labcorp catalog page

Panels that include this biomarker

  • Thyroid-stimulating Hormone (TSH) and Free T4 224576

    2 analytes · Serum · Fasting not stated · Turnaround Within 1 day

    Method and collection
    Method
    Electrochemiluminescence immunoassay (ECLIA)
    Collection
    If a red-top tube or plasma is used, transfer separated serum or plasma to a plastic transport tube.
    Labcorp catalog page

  • Long COVID Profile 165065

    52 analytes · Serum · Fasting not stated · Turnaround Within 1 day

    Method and collection
    Method
    See individual test components.
    Collection
    Serum: Separate serum from cells within two hours of collection. Urine: A voided specimen is usually suitable. If the specimen is likely to be contaminated, a clean catch midstream specimen is desirable. Whole blood: Invert tubes 8 to 10 times immediately after tube is filled at time of collection.
    Labcorp catalog page

Quest Diagnostics 1 test

Single-analyte tests

  • T4 Free (FT4) 866

    Serum · Fasting not stated · Turnaround Set up: Sun-Fri; Report available: 3 days

    Method and collection
    Method
    Immunoassay (IA)
    Reference notes
    <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
    Quest Diagnostics catalog page

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Goals and conditions

We link T4,Free(Direct) to these goals and conditions from named guidelines and studies.

Sources

Verify these ranges and sources

We compile this page from named laboratory catalogs, guidelines and studies. Labs calculate reference intervals from the people they test, for one assay method and one population group, so an interval describes that population rather than an optimal target.

Interpret your own results with a licensed clinician, or track your lab history and health goals in Aumnivida.

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