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T3, Free (fT3) details

What T3, Free (fT3) shows

Free T3 (fT3) measures the small, unbound, biologically active portion of triiodothyronine (T3) โ€” the more potent of your two main thyroid hormones โ€” available for your body's tissues to actually use. It's used alongside TSH and free T4 to evaluate thyroid function, and can be particularly useful in situations where T4-to-T3 conversion issues are suspected, or when TSH and free T4 results don't fully explain a person's symptoms, since free T3 is the hormone form most directly responsible for many of thyroid hormone's effects on metabolism.

Normal ranges

Typical adult range

2.3โ€“4.2 pg/mL

Most labs report a range close to this

Hormunity optimal range

3โ€“3.5 pg/mL

A narrower functional target

Each lab sets its own reference range. Always compare your result with the range printed on your report, and review it with a healthcare provider.

Tests that include T3, Free (fT3)

Labcorp Not offered
Quest Not offered
Quest Not offered
Quest Not offered
Quest Not offered
Quest Not offered
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