Free T3 and Free T4
The unbound, biologically active fraction of the thyroid hormones.
Also known as: FT3, FT4, free thyroxine, free triiodothyronine
Price on request
We can collect this sample at your home, free of charge. Book a home visit.
- Turnaround
- Same day
- Preparation
- No fasting needed. Eat and drink normally.
- Sample
- Blood sample
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About this test
Most thyroid hormone in the blood is bound to protein and inactive. The free fractions are what actually reach your tissues, so they give a truer reading when the binding proteins themselves are altered — in pregnancy, on the contraceptive pill, or in liver and kidney disease.
What it measures
- Free T3
- Free T4
A note on results. A single test is one part of a clinical picture, not a diagnosis. Discuss your report with a qualified doctor, who will read it alongside your history and examination.
Related to
- Thyroid
Often ordered with this
Anti-TPO Antibodies
Identifies autoimmune thyroid disease as the cause of an abnormal thyroid result.
- 24–48 hours
- No fasting
- Home collection
T3 and T4 (Total)
The two circulating thyroid hormones, measured alongside TSH to confirm an over- or under-active thyroid.
- Same day
- No fasting
- Home collection
Thyroglobulin
Used to monitor for recurrence after treatment for thyroid cancer.
- 3–5 working days
- No fasting
- Home collection