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UberTests

Free T4 Thyroid Hormone

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Free T4 may be indicated when binding globulin (TBG) problems are perceived, or when conventional test results seem inconsistent with clinical observations. It is normal in subjects with high thyroxine-binding globulin hormone binding who are euthyroid (ie, free thyroxine should be normal in nonthyroidal diseases). It should be normal in familial dysalbuminemic hyperthyroxinemia.

Quick facts

Sample type

Serum (preferred) or plasma

Turnaround

2–4 business days

Fasting

No Fasting Required

Doctor’s order included

Licensed physician review and requisition included with every test.

Free T4 Thyroid Hormone

  • Thyroid Function
  • General Health & Wellness
    • Cpt Codes
    • 84439

    what is Free T4 Thyroid Hormone and why is it important?

    Free T4 may be indicated when binding globulin (TBG) problems are perceived, or when conventional test results seem inconsistent with clinical observations. It is normal in subjects with high thyroxine-binding globulin hormone binding who are euthyroid (ie, free thyroxine should be normal in nonthyroidal diseases). It should be normal in familial dysalbuminemic hyperthyroxinemia.

    When to Consider a Free T4 Test

    • If you are experiencing symptoms commonly associated with thyroid dysfunction, including unexplained weight gain or loss, increased or decreased energy levels, sensitivity to cold or heat, dry skin, hair loss, anxiety, irritability, or depression.
    • When initial thyroid screening tests (like TSH) are abnormal, and a more specific assessment of active thyroid hormone levels is needed.
    • If your healthcare provider suspects a thyroid binding globulin (TBG) issue that might affect total thyroid hormone measurements but not the metabolically active free hormone.
    • As part of monitoring the effectiveness of thyroid hormone replacement therapy or anti-thyroid medication.

    Who Benefits from a Free T4 Test

    • Individuals who are experiencing symptoms related to thyroid imbalance, such as unexplained weight changes, persistent fatigue, changes in heart rate, or mood swings.
    • Those who are currently being treated for a thyroid condition and need to monitor the effectiveness of their medication.
    • People whose previous thyroid test results (e.g., TSH or total T4) were inconsistent with their clinical observations or symptoms.

    Commonly Used for Diagnosis of:

    • Hyperthyroidism: To assess overactive thyroid function, as Free T4 levels are typically elevated.
    • Hypothyroidism: To determine underactive thyroid function, often indicated by low Free T4 levels.
    • Subclinical Thyroid Dysfunction: To evaluate subtle thyroid imbalances where other tests like TSH might be borderline.
    • Thyroid Hormone Resistance: To help diagnose rare conditions where the body's cells do not respond properly to thyroid hormones.
    • Pituitary or Hypothalamic Disorders: To investigate conditions affecting the master glands that regulate thyroid function.
    • Monitoring Thyroid Treatment: Crucial for patients on thyroid hormone replacement or anti-thyroid medications to ensure optimal dosage and treatment effectiveness.
    • Investigating Thyroid Binding Globulin (TBG) Abnormalities: Free T4 provides a more accurate measure of active thyroid hormone when protein levels that bind thyroid hormones are abnormal.
    • Evaluating Non-Thyroidal Illness (NTI): To differentiate true thyroid disease from temporary changes in thyroid hormone levels due to severe illness or hospitalization.

    Caution

    Important Caution Regarding Free T4 Results

    It is important to discuss your Free T4 test results with a healthcare provider. Several factors, including certain medications (such as propranolol, amiodarone, heparin, or carbamazepine) and non-thyroidal illnesses, can influence Free T4 levels. A doctor can interpret your results in the context of your overall health, symptoms, and other diagnostic tests to provide an accurate diagnosis and appropriate treatment plan.

    Frequently Ordered Together

    How It Works?

    1
    Add Your Test to Cart and Check out

    once Test Order is received, Our physicians will review your request and email you the easy-to-follow requisition form.

    2
    Locate and Visit Your Nearest Laboratory

    Find the closest partner location—most are within 2–3 miles—and drop by for a quick, no‑appointment blood draw.

    3
    Get your Results Online

    Once your sample is processed, we’ll send your report straight to your inbox within 1–3 business days. Just click the link to view your results anytime.

    4
    Book a Optional Consult

    Have Questions about results? Book a phone or video visit with one of our doctors. They’ll walk you through your report, explain any findings, and recommend next steps