What is Liothyronine?
Your body makes two main hormones, thyroxine (T4) and tri-iodothyronine (T3). Thyroxine is a pro-hormone and needs to be converted to T3. It’s T3 that your body uses for many of its functions and is therefore called the active thyroid hormone. T3 is available for your body to use as it needs it.
Liothyronine is the man-made version of tri-iodothyronine (T3). For most people, levothyroxine is the perfect treatment and they become well. However, there is a small group of people who see little or no improvement on levothyroxine alone.
There has been a lot of research into liothyronine over the years. However, the research on whether the addition of liothyronine is helpful is inconclusive.
If you still feel unwell on levothyroxine, do check on the following before thinking about asking for a trial of T3 as they are very important points:
“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.”
“Our results require replication but suggest that commonly inherited variation in the DIO2 gene is associated both with impaired baseline psychological well-being on T4 and enhanced response to combination T4/T3 therapy, but did not affect serum thyroid hormone levels.”
Unfortunately, the NHS doesn’t do the DIO2 test but Regenerus Laboratories now do a private DNA panel that includes both DIO1 and DIO2 –https://thyroiduk.org/testing/private-thyroid-tests-in-the-uk/regenerus-labs-2/
Liothyronine medications
Liothyronine acts much more quickly than levothyroxine and sometimes needs to be taken twice a day for most people because it only lasts a few hours in the body before it runs out. At the moment there are no licensed brands of slow-release liothyronine although there are some compounded versions from specialist pharmacies.
There are various generics (copies of the original brands) of liothyronine manufactured by different pharmaceutical companies. These can vary in their ingredients. Some contain lactose and therefore for people who are lactose intolerant it’s best to find a lactose-free version. Some people are intolerant of some of the fillers and binders within the liothyronine tablet such as mannitol which can cause various side effects.
However, for most people, there will not be any problem when taking liothyronine. For those that do have problems with some of the ingredients, try to find out which generic/ingredient you are having issues with.
There are compounding pharmacies (pharmacies that make the tablet to order) that can make liothyronine tablets with very little or no fillers and binders or with fillers and binders that are less likely to cause problems.
Read more about common thyroid medications including ingredients.
What is the dosage of T3?
The dosage of T3 will depend on which clinician you visit. Some clinicians will prescribe 5mcg twice a day, some will prescribe 10mcg twice a day. Your levothyroxine will also be reduced so that you do not take too much thyroid hormone and suffer side effects.
If you do not find that T3 works for you, your clinician will usually withdraw the T3 and increase the levothyroxine back to the previous dosage.
We suggest that you make a note of any symptoms you have prior to taking T3 and make a note of your test results and the date of the test results including the range. This way, you can make a note of any of the symptoms that improve and you can use this as evidence for keeping you on T3.
Be aware that T3 has a short half life, meaning that the hormone runs out after a few hours. This means that for a lot of people, it is better to split the dosage and take it twice a day unless you take a sustained release capsule (although these are not available on the NHS at the moment). We know that some people find it’s better to take it three times a day. It’s often a case of trial and error to find what works for you.
The controversy surrounding liothyronine
There is a lot of controversy over the use of liothyronine now. In the past your GP could prescribe it but since the exorbitant increase in the cost a few years ago, the NHS created guidance that stated that it should not routinely be prescribed and that only endocrinologists can prescribe. However, some endocrinologists agree with its use and others don’t.
There have been various different guidelines across Europe and the UK over the years such as NICE, NHS England and the British Thyroid Association amongst others. These guidance documents tend to follow the NHS England Guidance. Unfortunately, local Integrated Care Boards (ICBs), who decide on which medications can be prescribed, seem to take “not routinely” to mean “should not be prescribed”.
Guidance documents
NICE – Thyroid disease: assessment and management (NG145) –
Published: 20 November 2019-
These are the relevant sections we need to be aware of in respect of liothyronine and NDT:
Managing primary hypothyroidism
1.3.3 Offer levothyoxine as first-line treatment for adults, children and young people with primary hypothyroidism
1.3.4 Do not routinely offer liothyronine for primary hypothyroidism, either alone or in combination with levothyroxine, because there is not enough evidence that it offers benefits over levothyroxine monotherapy, and its long-term adverse effects are uncertain.
1.3.5 Do not offer natural thyroid extract for primary hypothyroidism because there is not enough evidence that it offers benefits over levothyroxine, and its long-term adverse effects are uncertain.
Natural thyroid extract does not have a UK marketing authorisation so its safety is uncertain.
Thyroid UK along with other thyroid charities and organisations have campaigned really hard to get the two latest NHS England guidance documents aligned so that there is no confusion for ICBs and clinicians.
Unfortunately, NHS England feel that there is no confusion and so have refused to edit one of them.
Liothyronine (including Armour Thyroid and liothyronine combination products) (updated 2023) (page 37 in the pdf document)
In this guidance it states:
Recommendation:
In this guidance it states:
NHS England and NHS Confederation policy guidance, “Items which should not routinely be prescribed in primary care: policy guidance”, recommends that:
NOTE: It does not state:
We are very concerned that the guidance for ICBs states that it should not be initiated or that it should be deprescribed in patients currently prescribed this medication.
We are aware that many patients have either had their request for a trial refused and that other patients have either had their liothyronine withdrawn or that the dosage has been reduced.
We feel that it could be, in part, due to the guidance for ICBs being different to the guidance created for prescribers.
If you have an appointment with an endocrinologist or you contact your local ICB, do ensure that you discuss the correct guidance with them.
What can I do to campaign about this?
If you have either had your prescription withdrawn or you have been refused a trial of T3, do please write to the following organisations/people:
Do also let us know your story and we can collect them as evidence – https://thyroiduk.org/support-us/help-us-raise-awareness/share-your-story/
This guidance is primarily a document that gives many reasons why a patient should not be prescribed liothyronine. It goes into various different pieces of research explaining the negative side of the document and mentions a strong placebo effect of thyroid hormone.
However, their recommendations do include the following:
(e.g., 0.3–2.0 mU/L) for 6 months
Should I ask for a trial of liothyronine?
Absolutely yes, as long as you have checked all the points in this article. If you find that your vitamin/mineral levels are nearer to the bottom of the range than the top, do think about supplementing for three months to see if it helps.
Do ensure that your TSH is in the right place for you. Most people on levothyroxine find that the TSH needs to be right at the bottom of the range. If your level is like this, do visit your GP and discuss an increase in your levothyroxine to see if this helps. It’s much cheaper than T3 and it might make all the difference!
Do try and get all the relevant thyroid tests done including T3 although your GP may not be able to run a T3 test for you. In a lot of cases, NHS labs will refuse to do this test even if your GP asks for it.
If this happens, we have been told that the GP needs to ask for a “Miscellaneous Biochemistry” test and then put a note about testing T3. It seems that the people in the lab do not see the notes made on the blood form unless they are directed there by a request for a miscellaneous biochemistry test. However, this may not be the case in all areas so do let us know if this worked for you.
If you can’t get a T3 test on the NHS, we do work with a few private testing companies who will do T3 as part of a panel of tests. We have organised discounts for you with some of these companies.
Be aware that the NHS do not run the DIO2 test. This test can only be run as part of a private DNA test panel. We work with Regenerus Laboratories who do this test – https://thyroiduk.org/testing/private-thyroid-tests-in-the-uk/regenerus-labs-2/
Make sure that you get a referral to an endocrinologist who believes that some patients need T3. It would be a waste of your time to visit an endocrinologist who believes that patients do not need it.
If your GP refuses to make a referral for you, try going back again to ask but next time take someone with you who can advocate for you such as a friend or family member. We know that, sometimes, taking a male person with you has helped to persuade the doctor to do a referral!
We have heard reports that doctors say things like:
In response to these comments, you could say something like:
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Glossary
Endocrinologist – a medical practitioner qualified to diagnose and treat disorders of the endocrine glands and hormones
Genetic – relating to genes or heredity
Inconclusive – not leading to a firm conclusion or result; not ending doubt or dispute
Levothyroxine – a synthetic thyroid hormone commonly given to treat an under-active thyroid. It is also known as L-thyroxine
Liothyronine – Synthetic Triiodothyronine (thyroid medication)
Pro-hormone – a hormone that is changed into another hormone
Thyroxine – the main hormone secreted into the bloodstream by the thyroid gland. It is the inactive form
Date updated: 17.07.25 (V2.1)
Review date: 17.07.28
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