Free T3 (Triiodothyronine)
Free T3 is the biologically active form of thyroid hormone. It regulates metabolism, heart rate, and body temperature.
Test Information
Reports In
Same day (6 hours)
Parameters
1
Requisites
Blood Sample
Sample Type
Blood
Measures
Free triiodothyronine concentration
Identifies
Active thyroid hormone level, hyperthyroidism
What is the Free T3 Test?
Free T3 (Triiodothyronine) is the active thyroid hormone that directly affects your metabolism, heart rate, and body temperature. Only a small fraction of T3 circulates freely in blood — the rest is bound to proteins. Free T3 is the most potent thyroid hormone and is particularly important in diagnosing hyperthyroidism.
Why Should You Take This Test?
Measures active thyroid hormone. Useful when TSH is abnormal or to confirm hyperthyroidism.
Who Should Get Tested?
Abnormal TSH
Free T3 helps complete the thyroid picture.
Suspected Hyperthyroidism
T3 often rises before T4 in early hyperthyroidism.
Thyroid Medication Monitoring
Ensures optimal hormone levels.
Warning Signs — When Should You Get This Test?
Common Conditions Detected
Frequently Booked Together
Tests commonly ordered alongside Free T3 for a complete picture
TSH
Always interpreted alongside TSH
Free T4
Complete thyroid hormone assessment
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