Free T4 (Thyroxine)
Free T4 is the main hormone secreted by the thyroid. It reflects thyroid gland function and is converted to T3 in tissues.
Test Information
Reports In
Same day (6 hours)
Parameters
1
Requisites
Blood Sample
Sample Type
Blood
Measures
Free thyroxine concentration
Identifies
Thyroid hormone production, hypothyroidism, hyperthyroidism
What is the Free T4 Test?
Free T4 (Thyroxine) is the main hormone produced by the thyroid gland. Most T4 circulates bound to proteins — Free T4 is the unbound, active form available for use by your body's cells. It serves as a reservoir that gets converted to the more active T3 as needed. Free T4 is essential for diagnosing both hypo- and hyperthyroidism.
Why Should You Take This Test?
Essential for thyroid evaluation. Used with TSH to diagnose and monitor thyroid disorders.
Who Should Get Tested?
Abnormal TSH Results
Free T4 confirms and quantifies thyroid dysfunction.
On Thyroid Medication
Monitoring to ensure correct dosage.
Pregnant Women
Thyroid hormones are critical for fetal brain development.
Warning Signs — When Should You Get This Test?
Common Conditions Detected
Frequently Booked Together
Tests commonly ordered alongside Free T4 for a complete picture
TSH
T4 is always interpreted alongside TSH
Free T3
Complete thyroid hormone panel
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