Thyroid Blood Test Buying Guide

Understand the different types of thyroid blood tests and what they can tell you about your thyroid health.

Thyroid conditions are common, they are found in about 2% of the UK population and more than 5% of people over 60 [1].

In this guide, we look at the different thyroid tests that are available and what they can tell you about your thyroid health. 

In this guide, we include:

Why is the thyroid important?

The thyroid governs metabolism. Too much thyroid hormone (hyperthyroidism) speeds things up, causing symptoms like weight loss, feeling overly hot, fidgety, and anxiety. Too little (hypothyroidism) slows things down, leaving you exhausted, feeling cold and gaining weight or struggling to lose it. The risk of developing a thyroid condition is higher for women than men because most thyroid conditions are caused by an autoimmune disorder, which is more prevalent in women.

Why buy a private thyroid blood test?

The types of thyroid tests that are available from GPs in the UK can be limited. Often, they will only test thyroid-stimulating hormone (TSH) and free thyroxine (FT4).

Private thyroid tests give access to the full range of thyroid hormones, thyroid antibodies and nutrients that can affect thyroid health, together with the added advantage of convenient and speedy service.

What are the different types of thyroid blood tests?

1. Thyroid profiles and thyroid function tests

Most thyroid tests are bought as thyroid profiles, which are specially curated panels of tests designed to provide deeper insight into current thyroid function. Thyroid profiles can also identify the reason why the thyroid may be overactive or underactive.

Most thyroid profiles will test for thyroid-stimulating hormone (TSH), with either or both main thyroid hormones, thyroxine (T4) and triiodothyronine (T3), and can also include thyroid antibodies (thyroglobulin antibodies and thyroid peroxidase antibodies).

2. Thyroid profiles with general health and nutrition

Sometimes it isn’t enough to focus on thyroid function. This is especially true when investigating symptoms that could be associated with an underactive thyroid but could also be caused by other conditions such as iron deficiency anaemia, a nutritional deficiency, or a hormone imbalance. More advanced tests will also include relevant health and nutritional biomarkers.

Optimising some vitamins and minerals can also support thyroid function - so a thyroid profile that tests nutritional biomarkers like the B vitamins, ferritin, and vitamin D, can help manage a thyroid condition.

3. Single biomarker thyroid tests

It is possible to buy tests for individual thyroid hormones and thyroid antibodies. These tests usually complement other tests. If the GP has tested some of the thyroid hormones but did not test for thyroid antibodies, you may wish to test antibodies separately. This will help to establish whether an autoimmune condition could be the cause of a thyroid condition.

Testing thyroid hormones individually is not recommended unless done with other thyroid function tests as interpreting a single test in isolation may be limited.


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How do I choose the right thyroid blood test for me?

If you suspect that you have a thyroid disorder, the best way to investigate is by taking a thyroid blood test.

We have three popular tests which can help you understand whether a thyroid disorder is causing your symptoms.

1. Thyroid Function Blood Test

The Thyroid Function Blood Test is a comprehensive test that looks for TSH, FT4 and FT3 - the biologically active form of FT4. This test helps you to take a more in-depth look at your thyroid hormones.

Why this test?

The Thyroid Function Blood Test is for you if you want to investigate all your thyroid hormones, including FT3.

This test is also for people taking thyroid medication (including NDT and liothyronine) or who are still experiencing symptoms and want to check that T4 is converting to T3.

2. Thyroid Function with Antibodies Blood Test

Our Thyroid Function with Antibodies Blood Test tests for thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and thyroid antibodies.

If you have a family history of thyroid or autoimmune disease, you are more likely to develop one yourself. With this test, you can tell if your thyroid hormones are functioning within the healthy range. You can also detect any abnormalities caused by an autoimmune disease. Even if your thyroid function is currently normal, elevated antibodies may increase your risk of developing a thyroid disorder in the future.

Why this test?

The Thyroid Function with Antibodies Blood Test is for you if you suspect that you have a thyroid condition. Or, you have a family history of thyroid or autoimmune disease and want to check if you have elevated antibodies.

This test is also for people taking thyroid medication and who want to monitor their thyroid hormones and antibodies.

3. Advanced Thyroid Function Blood Test

This test includes the thyroid hormones, thyroid antibodies, and nutritional markers that can support thyroid function. If your nutritional markers are low, this can cause symptoms like a thyroid disorder. For example, low iron (ferritin), low vitamin D and low B vitamins can cause fatigue and low energy.

Why this test?

The Advanced Thyroid Function Blood Test is for you if you want to pursue several lines of investigation for your symptoms.

This test is also for people who have been diagnosed with a thyroid disorder and want to make sure that they are getting the nutrients that support thyroid function.

How often should I take a thyroid blood test?

How often you take a thyroid test will depend on your diagnosis and symptoms.

If you are monitoring your thyroid function, you should always take the test at the same time of day so that you can compare results properly. We recommend taking your thyroid function test in the morning before you have taken any thyroid medication.

  • Results normal – no symptoms  If you receive normal thyroid function test results and have no symptoms, there is no need to repeat the test. We advise repeating the test in the future if you develop symptoms that you think might be thyroid-related.
  • Borderline results – no symptoms – A borderline TSH is between 4 mlU/L and 10 mlU/L. At this level, TSH is above the normal range but below the level that a doctor would typically treat. If the thyroid hormones are within the normal range, and you aren’t experiencing any symptoms, we recommend testing your thyroid function annually. Having an elevated TSH does raise the risk that you will develop an underactive thyroid, so we advise repeating the test if you develop any symptoms.
  • Borderline results – with symptoms – If TSH is borderline (between 4 mlU/L and 10 mlU/L), the thyroid hormones are normal, but you are experiencing symptoms, we suggest repeating your test in 3 months. If you haven’t yet tested your thyroid antibodies, we suggest doing so with your next test. Elevated antibodies also raise the risk that you will develop an underactive thyroid. We would also recommend discussing your results and your symptoms with your doctor.
  • Known hypothyroidism – symptoms managed –With a diagnosed thyroid disorder and where symptoms are being managed, testing only need to happen annually or as recommended by the doctor.
  • Known hypothyroidism – with symptoms With a diagnosed underactive thyroid, where replacement hormones are being taken but symptoms persist, we suggest repeating a thyroid function test. We also recommend seeing your GP so that you can rule out other possible causes for the symptoms.
  • Known hypothyroidism – changed medication dosage – Once diagnosed with an underactive thyroid, it may take time to get the dose of thyroid replacement right. It is not unusual for symptoms to reappear even after taking medication, which may mean the dose will need adjusting. Too much thyroid replacement hormone could cause the metabolism to speed up, resulting in nervous anxiety, weight loss and sensitivity to heat. Too little thyroid medication, or if the thyroid condition worsens, could cause underactive thyroid symptoms like weight gain, sensitivity to cold and low energy. We recommend repeating a thyroid function test eight to 12 weeks after adjusting your dose.

Read more about your thyroid in our Thyroid Hub


  1. Ingoe, L., Phipps, N., Armstrong, G., Rajagopal, A., Kamali, F. and Razvi, S., 2017. Prevalence of treated hypothyroidism in the community: Analysis from general practices in North-East England with implications for the United Kingdom. Clinical Endocrinology, 87(6), pp.860-864.
  2. Gleicher, N. and Barad, D., 2007. Gender as risk factor for autoimmune diseases. Journal of Autoimmunity, 28(1), pp.1-6.
  3. Trivalle, C., Doucet, J., Chassagne, P., Landrin, I., Kadri, N., Menard, J. and Bercoff, E., 1996. Differences in the Signs and Symptoms of Hyperthyroidism in Older and Younger Patients. Journal of the American Geriatrics Society, 44(1), pp.50-53.
  4. Canaris, G. J., Steiner, J. F., & Ridgway, E. C. (1997). Do traditional symptoms of hypothyroidism correlate with biochemical disease? Journal of General Internal Medicine, 12(9), 544–550.

Related tests

Thyroid Function Blood Test

The Thyroid Function Blood Test checks your thyroid stimulating hormone (TSH), free T3 (FT3) and free T4 (FT4) to see if you have the right level of thyroid hormones for a healthy metabolism

  • Results estimated in 2 working days
  • 3 biomarkers
Thyroid Function with Antibodies Blood Test

The Thyroid Function with Antibodies Blood Test checks your thyroid stimulating hormone (TSH), free T3 (FT3) and free T4 (FT4), as well as thyroid antibodies, for an in-depth picture of your thyroid health

  • Results estimated in 2 working days
  • 5 biomarkers
Advanced Thyroid Function Blood Test

Get detailed insights into your thyroid function, including antibodies and nutrition, for optimum thyroid health

  • Results estimated in 2 working days
  • 10 biomarkers