Diagnosing and managing a thyroid condition

Understand how thyroid conditions are diagnosed and ways to manage a thyroid-related condition or disease.

Want to know more about how a thyroid condition is diagnosed and managed? Look no further. 

In this blog we discuss:

How are thyroid conditions diagnosed?

Feeling tired is a common symptom of a thyroid condition, but there are many more too. If you suspect that you have a thyroid condition or thyroid-related disease, your health investigations will usually involve a blood test.

Thyroid disease can be caused by different conditions, so diagnosing a condition isn’t always straightforward. But testing different thyroid-related hormones, vitamins, and minerals could hold the answers to the cause of your symptoms.

Diagnostic and screening procedures are regulated activities, and all formal diagnoses in the UK must come from a CQC registered doctor.

What are the different types of thyroid blood tests?

Thyroid blood tests range from a simple blood test that looks at related hormones only to an advanced test that looks at related vitamins, minerals, and thyroid antibodies.

Simple thyroid blood test

A simple test that measures levels of thyroid-stimulating hormone, FT4 and FT3 will give a complete picture of your thyroid hormone status.

Our Thyroid Function Blood Test examines your levels of thyroid hormones (FT3 and FT4), together with TSH, to check whether your thyroid is performing normally. It is common for doctors in the UK to only test for TSH levels when investigating symptoms, though, so always ask what is involved in a test first.

Thyroid blood tests can show:

  • Thyroid Stimulating Hormone (TSH) – TSH is produced in the pituitary gland and stimulates the thyroid to produce thyroid hormones T4 and T3. TSH is produced in response to circulating levels of T4 and T3. When levels of T4 and T3 are low, TSH production increases to stimulate the thyroid to produce more hormones. Raised TSH is commonly seen in underactive thyroid and low levels of TSH are seen in response to an overactive thyroid as the body tries to reduce the production of T4 and T3.
  • Free thyroxine (FT4) – FT4 is the amount of T4 that is not bound to proteins in the blood and is available to be used by the body’s cells where it is converted into T3. Low levels of FT4 may indicate an underactive thyroid whereas high levels may indicate an overactive thyroid.
  • Free triiodothyronine (FT3) – FT3 is the active thyroid hormone that regulates metabolism in the cells. FT3 is T3 that is not bound to proteins and is considered a better measure of the level of hormone that can be used by the cells. Low levels of FT3 are commonly seen in people with an underactive thyroid whereas high levels are seen with an overactive thyroid.

Thyroid antibody blood tests

A comprehensive blood test includes tests for thyroid antibodies, as well as hormones. Thyroid antibodies may help to explain whether an autoimmune disorder, such as Hashimoto's disease or Graves' disease, is the underlying cause of a thyroid condition.

Thyroid antibody blood tests can show:

  • Thyroglobulin antibodies (TGAb) – Thyroglobulin is a protein used by the thyroid gland to produce T3 and T4. Ordinarily, it does not enter the bloodstream, but if your thyroid is inflamed or under attack from your immune system, thyroglobulin can be secreted, and antibodies detected. Raised levels of thyroglobulin antibodies can indicate autoimmune thyroid disease.
  • Thyroid peroxidase antibodies (TPOAb) – The thyroid gland produces the enzyme thyroid peroxidase, which is required to produce thyroid hormones. A TPOAb blood test looks for antibodies in the blood that target the thyroid peroxidase enzyme. High levels of antibodies indicate that the immune system is attacking the thyroid gland and impairing its function. Raised levels of TPOAb are often found in Hashimoto's disease and many cases of Graves' disease.

If you want to know more about thyroid antibodies and thyroid antibody blood test results, see our blog: all you need to know about thyroid antibodies

Advanced blood tests

The most advanced thyroid blood tests will also contain tests for thyroid nutrition – such as ferritin (iron stores), folate, vitamin B12 and vitamin D.

Having optimal levels of these vitamins and minerals can help support your thyroid function. Deficiencies can cause symptoms like those of a thyroid disorder. Testing these markers helps to determine whether your symptoms are caused by a condition or a nutritional deficiency.

Advanced blood tests can show:

  • Ferritin – Ferritin is a complex globular protein that stores iron in an inactive form. As your iron stores deplete, the ferritin releases iron for use. If your ferritin depletes, you will run out of iron and your ability to produce red blood cells in your bone marrow decreases. Ferritin gives a good measure of your iron stores and, as an acute-phase protein, it can increase during periods of infection, inflammation, or trauma.
  • Folate – Serum – Folate is a B vitamin that acts as a coenzyme in the metabolism of amino acids. It is vital for the synthesis of purines and pyrimidines, which are essential for DNA synthesis and red cell formation. Folate is especially important during the first trimester of pregnancy. This vitamin, along with other B vitamins, plays an important role in regulating energy by modulating the synthesis and breakdown of carbohydrates, fat, protein, and other bioactive compounds.
  • Vitamin B12 – Active –Vitamin B12 is important for producing red blood cells, which carry oxygen around the body. B12 is also involved in metabolism and the nervous system and prolonged lack of vitamin B12 may cause nerve damage. Although vitamin B12 is almost entirely found in animal-based foods, many vegetarian and vegan products are now fortified with vitamin B12.
  • Vitamin D – Vitamin D is vital for bone maintenance, along with calcium. It supports muscle function and protein synthesis and has non-musculoskeletal benefits, like immune modulation, protection against chronic diseases and increased athletic performance. Your skin can make vitamin D when it is exposed to sunlight. However, it is common for people living in the UK to be low in vitamin D, even if they exercise outside.

Check out our range of Thyroid Blood Tests or read our Thyroid Blood Test Buying Guide if you need help choosing which test is most suitable for you.

How to manage a thyroid condition

There are different ways to manage a condition, whether you have an overactive or underactive thyroid, or if you are experiencing thyroid-related symptoms.

1. Identify underlying health issues

If you are unsure whether your symptoms are thyroid-related, it is worth trying to find out other underlying health issues that might be causing your symptoms.

A comprehensive blood test can give you a good picture of your overall health. This could include your blood cells, kidneys, liver function, diabetes, iron status and vitamin B12/folate for anaemia, C-reactive protein (CRP) for inflammation and vitamin D.

2. Optimise vitamins and minerals

There is evidence that people with a diagnosed condition may have lower levels of certain nutrients.

Vitamins and minerals for thyroid conditions include:

  • Selenium – Low levels of selenium are associated with increased rates of hypothyroidism and with the development of some thyroid diseases. However, too much selenium can lead to selenosis, a condition that in its mildest form can lead to loss of hair and nails. If you eat meat, fish, or nuts, you should be able to get all the selenium you need from your daily diet.
  • Iron – Iron is one of the most important minerals for thyroid function. Iron deficiency can decrease the body’s response to TSH and cause lower levels of T3 and T4.
  • Zinc – Zinc is an essential trace element involved in thyroid hormone metabolism. Zinc supplementation has been shown to improve thyroid hormone levels in overweight or obese people [1].
  • Vitamin B12 – Vitamin B12 deficiency and pernicious anaemia are common in people with hypothyroidism. Pernicious anaemia is easy to overlook so we recommend testing for it if you are found to have low vitamin B12 levels.
  • Iodine – Iodine levels that are too low or too high can interfere with thyroid function. Iodine deficiency is rare in the UK, and some over-the-counter iodine supplements contain high levels, which could push your blood levels above the top end of the normal range. Excess supplementation can cause an increase in thyroid antibodies in some people.

If you are planning to take vitamin or mineral supplements, then make sure you keep within the recommended ranges – sometimes too much supplementation can be as harmful as not enough. Always consult your doctor before making any major dietary changes.

3. Manage stress

High levels of TSH are associated with high levels of cortisol, the hormone your body produces when under stress[2].

You can check your cortisol levels with a cortisol saliva test. This can detect slight increases in cortisol which are due to high levels of stress, as well as more serious abnormalities of cortisol.

Adopting relaxation techniques like meditation, getting regular and high-quality sleep, as well as adopting a healthy diet and exercise plan can help to relieve stress and correct mild abnormalities in cortisol levels.

4. Thyroid medication

Hypothyroidism is almost always treated using synthetic thyroid hormones that replace the hormones that the thyroid gland is struggling to produce.

Levothyroxine (synthetic T4) is commonly prescribed by GPs in the UK to people with an underactive thyroid to boost their levels of thyroxine. How you respond to medication will vary and depend on dosage – it can often take months to find the right dose of levothyroxine to alleviate your symptoms. It is common to monitor hormone changes while starting medication with a thyroid function test to understand and control the effects that varying doses have on your hormones.

Generally, levothyroxine will help to improve the symptoms of an underactive thyroid. For some though it doesn’t work, and this usually occurs when there is a problem in converting inactive T4 to active T3 in the body. Some practitioners will prescribe liothyronine (synthetic T3) either on its own or alongside levothyroxine to boost levels of T3 directly. Studies show that for most people there is no benefit in taking T3 instead of levothyroxine.

Some people who are struggling to control their thyroid symptoms with levothyroxine alone may experience an improvement when taking T3. Drugs, generally belonging to the class thioamides, are used to treat overactive thyroids and work by reducing the levels of thyroid hormones produced by the thyroid gland.

We recommend that any medical treatment of a thyroid condition is started under the guidance of a specialist and is carefully monitored and managed.


1.  Mahmoodianfard, S., Vafa, M., Golgiri, F., Khoshniat, M., Gohari, M., Solati, Z. and Djalali, M., 2015. Effects of Zinc and Selenium Supplementation on Thyroid Function in Overweight and Obese Hypothyroid Female Patients: A Randomized Double-Blind Controlled Trial. Journal of the American College of Nutrition, 34(5), pp.391-399.

2.  Macmillan.org.uk. 2022. Thyroid cancer - symptoms, types, treatment options. [online] Available at: <https://www.macmillan.org.uk/cancer-information-and-support/thyroid-cancer> [Accessed 4 March 2022].

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