Diagnostics·Diagnostics
Free T4 test
Informed by recognized medical guidance
Overview
A Free T4 test is a blood test that measures the amount of free thyroxine (the active form of a thyroid hormone) in your blood. It helps doctors check how well your thyroid gland is working and diagnose thyroid disorders such as an overactive or underactive thyroid.
Key facts
- T4 is one of the main hormones produced by the thyroid gland.
- 'Free T4' means the part of T4 not attached to proteins, which is the active form.
- This test is often done together with a TSH test for a complete picture of thyroid health.
- Abnormal Free T4 levels can indicate hyperthyroidism (overactive) or hypothyroidism (underactive).
Yes, Free T4 testing is very common. Many people with symptoms of thyroid problems or who have an abnormal TSH will have this test.