About Private Testing

There are various tests available for the diagnosis of thyroid disease including thyroid stimulating hormone (TSH); Free T4 (Free thyroxine); Free T3 (Free tri-iodothyronine); thyroid peroxidase antibody (TPO) and thyroglobulin antibody (TgAb).

NHS GPs in the UK generally only test for TSH to diagnose thyroid disease although in some areas of the country, the FT4 is tested too.

Some GPs test for thyroid antibodies but many feel that this is not necessary.

Testing for FT3 to diagnose hypothyroidism is very rarely undertaken by GPs.

Once a patient starts on treatment, NICE guidance states:

1.4.1 Aim to maintain TSH levels within the reference range when treating primary hypothyroidism with levothyroxine. If symptoms persist, consider adjusting the dose of levothyroxine further to achieve optimal wellbeing, but avoid using doses that cause TSH suppression or thyrotoxicosis.

1.4.3. For adults who are taking levothyroxine for primary hypothyroidism, consider measuring TSH every 3 months until the level has stabilised (2 similar measurements within the reference range 3 months apart), and then once a year.

1.4.4. Consider measuring FT4 as well as TSH for adults who continue to have symptoms of hypothyroidism after starting levothyroxine.

However, unfortunately, FT4 testing is not always carried out.

FT3 testing is very rarely carried out by GPs because either it is felt that it is not necessary or the GP asks for this and the laboratory send the results back without the FT3 test, possibly because the local Integrated Care Board Guidance is that it should not be tested. However – you can’t tell if a patient is converting their thyroxine effectively without an FT3 test. 

We know that in other countries all the thyroid tests are carried out including ultrasound testing and for a lot of patients, this would be the ideal in order that a firm diagnosis is made, including whether they have Hashimoto’s disease.

There is, however, more interest now from some researchers and clinicians in patients who do not resolve all of their symptoms on levothyroxine, and more research into combination treatment of levothyroxine and liothyronine is planned probably due to a recommendation from NICE in the Guidance for Thyroid Disease – https://www.nice.org.uk/guidance/ng145/chapter/Recommendations-for-research.

Thyroid UK believes that patients need to take control of their health if they can and this includes learning more about their condition, making sure that they take their medication correctly, monitoring their own health e.g. keep notes, and learn about thyroid testing.

Often, doctors will say, “Your results are normal” but we know that different people feel much better at a certain position with the test ranges. 

The British Thyroid Association guidance now states:

“In those with established overt hypothyroidism, levothyroxine doses should be

optimised aiming for a TSH in the 0.3–2.0 mU/L range for 3 to 6 months before a

therapeutic response can be assessed. In some patients, it may be acceptable to have

serum TSH below reference range (e.g. 0.1–0.3 mU/L), but not fully suppressed in

the long term.”

Many patients are not aware of this.

If a patient wants to monitor their thyroid health more frequently than their clinician or if a particular test is not available on the NHS, they have two options open to them –

either visit a private clinician, which can be expensive, ask for a referral to an endocrinologist who may organise FT3 testing or organise private testing for themselves. 

Until FT3 testing becomes standard in the NHS, and we believe it will, patients may want to check their own levels by self testing if they can afford it.

We appreciate that some people may not be able to afford private testing themselves but we know that private testing has been very helpful to a lot of people who can afford it and so we need to help them too.

In many cases, we have organised discounts for people with testing companies and in some cases, people would not be able to access private testing with some of the companies unless we help them to do this.

Be aware that if you take private test results to your GP or endocrinologist, they may not accept them.  Some doctors do accept them or, in some cases, will then organise an NHS test to confirm the result.

At least if you have a private test that shows you need a change in treatment, you are taking control and you know what you need to fight for.

Thyroid UK also firmly believes that patients should make healthy choices in respect of their diet not only regarding obesity but in respect of nutrition.

Poor nutrition is not only a cause of obesity.  It can also impact on thyroid health and we see many people with vitamin and mineral deficiencies that could be causing low levels of thyroid hormone or have very similar symptoms to an underactive thyroid such as vitamin B12 deficiency.

Vitamin D is often low in people with hypothyroidism/Hashimoto’s disease and in those who spend a lot of time indoors, even in the summer and people do not often realise that this may be a cause of some of their symptoms so checking this vitamin can be a very good idea.  People often do not want to bother their GP with this testing and it’s quick and convenient to test and monitor at home.

Thyroid UK, therefore, also suggests testing for nutritional status such as vitamin D, vitamin B12 and ferritin, which is not always available from clinicians on a regular basis.

Clinicians are extremely busy and have tight budgets.  Therefore, if patients are willing and able to pay for private blood tests, patients can monitor their health more closely.

Private testing laboratories inform patients if they are outside of any of the ranges.

Thyroid UK believes that if this is the case, the patient should make an appointment with their clinician to discuss their results and we firmly state this in our patient information.

We are aware of a number of cases where the patient has taken the results of their private tests to their clinician (GP and/or Endocrinologist) which has resulted in an amended treatment plan as it revealed issues not apparent from the NHS tests alone.

Thyroid UK checks that the testing laboratories we work with and their providers have the necessary accreditation and that the tests have been validated to ensure good quality of testing and management.

More information about the testing laboratories and their providers is available on request.

Date created: 02.09.25 (V1.6)

Review date:  18.03.28