LabwiseFree T4ng/dL
Free T4 is the unbound, active portion of the thyroid hormone thyroxine. It is usually read together with TSH.
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What Free T4 measures
Free T4 is the unbound, active portion of the thyroid hormone thyroxine. It is usually read together with TSH.
If your Free T4 is low
Free T4 below the range with a high TSH is commonly associated with an underactive thyroid.
Commonly associated with
- Underactive thyroid
- Pituitary function
- Severe illness
If your Free T4 is high
Free T4 above the range with a low TSH is commonly associated with an overactive thyroid or thyroid medication; with a typical TSH it is often a laboratory or binding-protein effect.
Commonly associated with
- Overactive thyroid
- Thyroid medication
- Biotin supplements affecting the assay
Typical reference range
| Group | Typical range |
|---|---|
| Adults | 0.82 – 1.77 ng/dL |
Typical adult values used by many US labs. Your own report prints the range your lab validated for its method, and that range is the one that counts. Labwise always uses the printed range first.
If it is within range
Your free T4 is within the range printed by your lab.
Also listed as
T4, Free, T4,Free(Direct), Thyroxine (T4), Free, FT4, Free Thyroxine, T4, Free (Direct)
Related tests
This page is general information about what a laboratory test measures and what results outside a reference range are commonly associated with. It is not medical advice, does not diagnose any condition and does not replace your clinician. Discuss your results with your healthcare provider.