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).
This test is for individuals who have symptoms of either an underactive or an overactive thyroid and want to assess whether their thyroid is producing too much or too little thyroxine. It can also be used to monitor an already diagnosed thyroid disorder.
We send you an easy-to-use kit to collect your blood sample.
Post your sample to our lab in the prepaid envelope provided.
View results securely in your own personal dashboard.
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.
T4 (Thyroxine) is the main hormone produced by the thyroid gland. T4 is not biologically active, and must be converted to T3 before it can become active in regulating metabolism. Some T4 is bound to proteins, while some T4 is 'free' or unbound. This test measures the level of total T4 in your blood.
Raised T4 can indicate an overactive thyroid while low T4 may indicate that the thyroid is struggling to produce sufficient thyroid hormones.
We will send you your Thyroxine (T4) finger-prick blood test sample collection kit which contains everything you need to take your blood sample in the comfort of your own home. If you are unsure about completing a finger-prick blood sample collection you will have the opportunity to select a clinic-based venous blood sample collection or choose to go our London laboratory during the checkout process.How to collect a finger-prick blood sample
Your Thyroxine (T4) test includes 1st class postage and packaging for you to send your blood sample directly to our laboratory for analysis. If you live in an area where you cannot rely on the post or you simply want to ensure that your sample arrives at the laboratory the following day, you may wish to send your blood sample guaranteed next day delivery for extra reassurance.
Your blood sample will be analysed at one of our chosen laboratories. You can be assured of fast, accurate results from one of our accredited independent providers of clinical diagnostic tests.
Our medical team will comment on out-of-range blood test results and give you follow-up advice where necessary. If you need it, a PDF copy of your Thyroxine (T4) test results can be downloaded for your doctor.
Once you have placed your order you will receive login details to mymedichecks.com where you can manage your account, track your orders and view your Thyroxine (T4) test results.
Stay motivated by filling in your online health and lifestyle questionnaire and seeing how improvements in your lifestyle can influence your test results. Your medical and family history gives us vital information when interpreting your results.