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What does your
Free T4 (Thyroxine) result mean?

Thyroid
⚠️ Educational only. LabPlain does not provide medical advice or diagnosis. Always discuss your specific results with your healthcare provider.
What this test measures

The Free T4 (Thyroxine) test measures the active, unbound form of the main thyroid hormone — it directly reflects how much thyroid hormone is available to your cells.

Normal reference range
0.8–1.8 ng/dL

Reference ranges can vary slightly between labs. Always compare your result to the range printed on your own lab report.

What your result might indicate
↑ If High

High Free T4 suggests an overactive thyroid (hyperthyroidism), which can cause anxiety, weight loss, and a racing heart.

↓ If Low

Low Free T4 confirms an underactive thyroid (hypothyroidism), often causing fatigue, weight gain, and feeling cold.

What to do next
Free T4 is most useful when interpreted alongside TSH. Together, they give a much clearer picture of thyroid function than either test alone.

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