Thyroid

Free T4

The unbound form of thyroxine available to tissues.

thyroidhormonesmetabolismlipids

About this biomarker

Free T4 measures the portion of thyroxine not bound to proteins in the blood. It is used with TSH to assess thyroid status.

Why it matters

It helps clarify thyroid hormone levels when TSH is abnormal or symptoms suggest a thyroid issue.

What lower levels may suggest

Low free T4 may suggest an underactive thyroid pattern.

What higher levels may suggest

High free T4 may suggest an overactive thyroid pattern.

Common tests

Free T4, thyroid panel, reflex thyroid testing

Your trend

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Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.