What Is a Normal Free T3 Level?
The normal Free T3 range is 2.3–4.2 pg/mL. Values below or above this range may indicate a condition that requires further evaluation.
Reference Range Table
| Marker | Low | Normal | High |
|---|---|---|---|
| Free T3 | Below 2.3 pg/mL — poor T4 conversion or hypothyroidism | 2.3–4.2 pg/mL | Above 4.2 pg/mL — hyperthyroidism or T3 supplementation |
What Affects Your Results
T3 medication or supplements, severe illness ("sick euthyroid syndrome" lowers T3), caloric restriction, stress, liver disease (impairs T4-to-T3 conversion), and certain medications.
When to Retest
Alongside TSH and Free T4 during thyroid medication adjustments. Not always needed for routine monitoring if TSH and Free T4 are sufficient.
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