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Total Thyroxine (T4) Blood Test
Total Thyroxine (T4) Blood Test
Total Thyroxine (T4) Blood Test
Total Thyroxine (T4) Blood Test

Total Thyroxine (T4) Blood Test

Thyroxine (T4) is the main hormone produced by the thyroid gland. This blood test measures levels of T4 to help in the diagnosis of thyroid disease.
Blood sample 1 biomarker included 2 working days turnaround

What's included?

Biomarker profile

  • Thyroid Hormones

Thyroid Hormones (1 Biomarker)

To produce thyroxine, the thyroid gland needs iodine from the food we eat. Thyroxine is called T4 because it contains 4 atoms of iodine. Although it is the most plentiful of the thyroid hormones, it is not biologically active and does not govern metabolism in our cells. That job is undertaken by triiodothyronine, or T3. T4 converts to T3 by the removal of an atom of iodine.

Thyroxine is typically measured in thyroid function tests because a low T4 reading is likely to indicate insufficient levels of T3 (and therefore a slow metabolism) while high levels of T4 tend to lead to excess T3 (resulting in an overactive metabolism).

Dr Sam Rodgers MBBS, MRCGP

3 simple steps

  • Take the test

    Take the test - either using your kit or visit a clinic.
  • Post your sample

    Send your sample in the freepost pack to our fully accredited lab.
  • Get your results

    Get your doctor reviewed results on
Expert interpretation<br>
of your results

Expert interpretation
of your results

One of our team of doctors will review your results and give you personalised advice based on your medical history, lifestyle and health and fitness goals.

Your personal<br>
health centre

Your personal
health centre

Discover the easy way to track your health through our online portal, View your results with doctor's advice, monitor any changes over time and see the improvements you can make to your health with simple lifestyle changes.

Questions? Let us help

Questions? Let us help

Our customer care team are on-hand to help you find the test that's right for you. Get in touch via phone, live chat or email.

Laboratories you can trust

Trusted by the NHS and private clinics alike, you can be sure of the highest testing standards from our partner laboratories

What our customers say

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Our tests are not a substitute for seeing your doctor, especially if you are suffering symptoms. Our doctors will interpret your results based on the information you have provided, but will not diagnose, consult or provide any treatment. You will be advised to see your doctor for any necessary follow-up action.