Thyroxine (t4)

This is an important test used to diagnose thyroid problems.

Finger-prick blood
1 tests included
2 days turnaround



About Thyroxine (t4)

What is free T4?

Thyroxine (T4) is a hormone produced by the thyroid gland, it is one of the two main thyroid hormones (with T3 being the other), which regulate metabolism throughout the body.

T4 acts both as a hormone by itself and as a precursor for T3 production. The vast majority of T4 in the body is bound to other proteins, with the remaining unbound T4 called free T4.

Measuring T4 gives an indication of thyroid function. Abnormal levels of T4 can indicate thyroid problems such as hyperthyroidism or hypothyroidism.

Why take the test?

This test measures the level of T4 in the blood. It is typically used to diagnose thyroid problems.


What's tested

Thyroid Function

How it works



Purchase your Kit

Just order a test online and get your kit delivered right to your door unless you are ordering a COVID-19 Fit to Fly test where you will be given appointment options to attend our clinics across the United Kingdom for a nose and throat swab PCR test at the checkout stage.



Take your test and post

Follow our simple instructions to take your sample and post back the enclosed prepaid envelope to our accredited lab for processing. We also offer home or workplace visits by a qualified nurse. For COVID-19 Fit to Fly tests you must attend one of our partner clinics for our trained collection officers to take your sample. You will then have the results emailed to you.



Get results directly to your dashboard

You will receive an email notification from our medical team when your results are available on your secure personalised health dashboard.