Free thyroxine (T4) blood test in Liverpool

Get an Free thyroxine (T4) blood test delivered straight to your door in Liverpool. Track what’s going on inside your body and improve your health.

Did you know?

A Liverpool physician, called Matthew Dobson, discovered the link between diabetes and sugar in 1774.

What is free thyroxine (FT4)?

Thyroxine (T4) is the main hormone produced by your thyroid gland. Most of the T4 in your blood is bound to protein — meaning it's inactive and your body can't use it. A small amount is unbound (free). So by measuring your free T4 levels, it gives you a more accurate picture of your thyroid function.

What is its function?

Your body converts T4 to another hormone called triiodothyronine (T3). T3 helps control your metabolism — like regulating your heart rate, body temperature, and breathing.

What can cause it to change?

If your thyroid produces too much or too little T4, it can lead to hypothyroidism (an underactive thyroid) or hyperthyroidism (an overactive thyroid).

Low T4 Low T4 levels might be caused by:

  • autoimmune thyroiditis — your body produces antibodies that attack your thyroid gland, like Hashimoto’s disease
  • treatment for an overactive thyroid
  • treatment for thyroid cancer
  • postpartum thyroiditis — your thyroid becomes inflamed within the first year after pregnancy
  • iodine deficiency
  • medications containing iodine e.g. amiodarone

High T4 High T4 levels might be caused by:

  • Graves’ disease — an autoimmune disorder
  • lumps (nodules) on your thyroid
  • goitre — swelling of your thyroid gland
  • postpartum thyroiditis
  • medications containing iodine

Your FT4 levels can increase two hours after taking levothyroxine (a medication to treat an underactive thyroid). Or if you're over or under-treating an existing thyroid condition with medication, your levels could be out of range. Biotin (vitamin B7) might also affect your levels. It's best to take your blood sample first thing in the morning in a fasting state.

What are the most common symptoms?

Low T4 If your thyroid is underactive, common symptoms include:

  • tiredness
  • weight gain
  • depression
  • constipation
  • dry skin
  • brittle hair
  • sensitivity to cold
  • memory problems
  • muscle aches
  • hoarse voice

High T4 If your thyroid is overactive, common symptoms include:

  • weight loss
  • increased appetite
  • excessive sweating
  • sensitivity to heat
  • twitching
  • fatigue
  • irritability and anxiety
  • heart palpitations
  • difficulty sleeping

In women, high or low thyroid hormones might affect your periods — for example, heavy or irregular periods.

What can I do to change my levels?

There are a number of nutrients that are important for your thyroid function:

  • Iodine — needed to make thyroid hormones
  • Zinc — needed to make thyroid hormones
  • Selenium — needed to thyroid hormones
  • Iron — plays an important role in thyroid hormone metabolism
  • Vitamin D — plays an important role in your immune function and low levels are linked to autoimmune thyroid disorders

If your levels indicate you have a thyroid disorder, it’s important to work with your doctor to come up with a treatment plan.

What is Thriva?

We’re a subscription-based health tracking company. With our blood testing kits you can take control of your health and see exactly what’s happening inside your body. Learn what lifestyle really works for you and improve everything from your sleep and energy levels to your heart health.

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Get your Thriva kit

Order your test online. We’ll post your kit the next working day via Royal Mail first class delivery.

Test kit contents

Perform your test

Your kit contains everything you need for your simple finger-prick blood test. When you’re done, use the freepost envelope to send it back.

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Results within 48 hours

Your full results, along with a personalised report from a qualified GP, will be available to access online.

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