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Thyroid
Free T4
Measures the active thyroid hormone that circulates freely.
What it measures
It measures the amount of free thyroxine in the blood.
Why it is tested
It is commonly used to assess thyroid hormone levels more directly.
Low results
Low results may be associated with an underactive thyroid or pituitary disease.
High results
High results may be associated with an overactive thyroid.
Related tests
TSH, Free T3, Thyroid peroxidase antibodies
Sources
Other markers
Disclaimer
This information is for education only and is not a substitute for medical advice. Results should be interpreted by a qualified clinician alongside your symptoms and medical history.