Free T4
Understand Free T4 levels for thyroid gland function evaluation. Monitor hormone balance for metabolic health optimization.
What is Free T4?
Free T4 measures the unbound, metabolically active portion of thyroxine hormone in your blood. Unlike total T4, free T4 is not affected by protein binding and provides a more accurate assessment of thyroid hormone availability to your tissues.
Why is it Tested?
Doctors order free T4 to evaluate thyroid function, diagnose hyperthyroidism or hypothyroidism, monitor thyroid hormone replacement therapy, and assess thyroid function during pregnancy. It’s often the preferred thyroid hormone test because it’s unaffected by binding proteins.
Normal Ranges
Reference ranges for free T4:
- Normal: 0.8–1.8 ng/dL
Optimal levels for symptom relief are often in the upper half of the reference range.
Reference ranges vary by authority. Track yours across multiple standards with automatic unit conversions in LabsVault.
What do Abnormal Results Mean?
Abnormal results are not a diagnosis. Always discuss your results with a qualified healthcare provider before making any medical decisions.
Low Free T4
Reduced levels may indicate:
- Hypothyroidism
- Insufficient thyroid medication
- Pituitary dysfunction
- Severe illness
- Certain medications
High Free T4
Elevated levels suggest:
- Hyperthyroidism
- Excessive thyroid medication
- Thyroiditis
- Graves’ disease
- Toxic nodular goiter
How to Track Over Time
Free T4 levels help optimize thyroid hormone replacement therapy and monitor thyroid disease progression. Changes typically occur more rapidly than TSH adjustments, making free T4 useful for evaluating recent medication changes or acute thyroid conditions.
Track your Free T4 results over time
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