Thyroid Blood Test Buying Guide

Thyroid conditions are common; they're 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 cover:

• Why is the thyroid important?
• Why buy a private thyroid test?
• What are the different types of thyroid tests?
• How do I choose the right thyroid test for me?
• How often should I take a thyroid test?
   

Why is the thyroid important?
 

The thyroid governs metabolism. Too much thyroid hormone (hyperthyroidism) speeds things up, causing symptoms like weight loss, heat sensitivity, hand tremors, and anxiety. Too little (hypothyroidism) slows things down and can cause symptoms such as fatigue, weight gain, and dry skin. 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 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 a 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 insights into current thyroid function. Thyroid profiles can also identify the reason why the thyroid may be overactive or underactive.

Most thyroid profiles will check thyroid-stimulating hormone (TSH), and either or both main thyroid hormones, thyroxine (T4) and triiodothyronine (T3). They may 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's possible to buy tests for individual thyroid hormones and thyroid antibodies. These tests usually complement other tests. If your 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 establish whether an autoimmune condition could be the cause of a thyroid condition.

However, testing individual thyroid hormones isn't recommended, unless performed alongside other thyroid function tests, as interpreting a single test result in isolation gives limited insights.

 

 

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

If you suspect 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.

It's also suitable if you're taking thyroid medication (including NDT and liothyronine) or 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 measures 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're more likely to develop one yourself. This test checks whether your thyroid hormones are 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 have a family history of thyroid or autoimmune disease and want to check if you have elevated antibodies.

It's also suitable if you're taking thyroid medication and want to monitor your thyroid hormones and antibodies.

3. Advanced Thyroid Function Blood Test

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

It's also suitable if you've been diagnosed with a thyroid disorder and want to make sure you have healthy nutrient levels to 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. Monitoring your thyroid condition with regular thyroid blood tests is important for managing symptoms and reducing complications. The National Institute for Health and Care Excellence (NICE) recommends annual testing [5], but you may require testing more frequently if your hormone levels are unstable or not well controlled.  

Regular blood tests can help your doctor assess the effectiveness of treatment and make necessary adjustments to your medication. They can also help pick up any vitamin deficiencies or other conditions that could be causing unwanted symptoms.

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

• Results normal – no symptoms –  if you receive normal thyroid function test results and have no symptoms, there's 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 result 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 your 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 level does raise your risk of developing an underactive thyroid, so we advise repeating the test if you develop any symptoms.
• Borderline results – with symptoms – If your TSH result is borderline (between 4 mlU/L and 10 mlU/L), your thyroid hormone levels are normal, but you're experiencing symptoms, we suggest repeating your test in three months. If you haven’t tested your thyroid antibodies, we suggest doing so with your next test. Elevated antibodies can increase your risk of developing an underactive thyroid. We also recommend discussing your results and symptoms with your doctor.
• Diagnosed hypothyroidism - with symptoms managed - annual testing or as recommended by your doctor.
• Diagnosed hypothyroidism – with symptoms – if you're taking replacement hormones 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 of your symptoms.
• Diagnosed hypothyroidism – changed medication dosage – following diagnosis, it can take time to get your medication dosage right. It's not unusual for symptoms to reappear even after taking medication, which may mean the dose needs adjusting. Too much thyroid hormone replacement could cause your metabolism to speed up, resulting in symptoms such as anxiety, weight loss, and sensitivity to heat. Too little thyroid medication, or if your 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. 

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References

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.
5. Recommendations: Thyroid disease: Assessment and management: Guidance (no date) NICE. Available at: https://www.nice.org.uk/guidance/ng145/chapter/recommendations (Accessed: 31 May 2023).