Natural desiccated thyroid (NDT) is the treatment that used to be given before levothyroxine came onto the market. It comes from pigs’ glands and contains both thyroxine (T4) and tri-iodothyronine (T3), although it has more T3 than the human thyroid produces.
American and Canadian brands of NDT are now available in the UK. The American brands are Armour Thyroid, NatureThroid, WP Thyroid and NP Thyroid. There is one Canadian brand, ERFA Thyroid.
Because natural desiccated thyroid has been around for so long it never needed to go through the licensing process in America – it was classed as a “grandfathered drug”. It has always been approved by the Food and Drug Administration (FDA) but not licensed in the same way that many other drugs have been.
Although there is long-standing evidence that levothyroxine is equal in efficacy to NDT, and there are studies that have found some patients do better on Armour thyroid, there are many doctors who do not like the idea of prescribing NDT. Unfortunately, there are no randomised controlled trials using NDT.
NICE guidance states:
NHS England has two sets of guidance documents. One for the Integrated Care Boards and one for prescribers:
NHS England guidance (https://www.england.nhs.uk/medicines-2/items-which-should-not-be-routinely-prescribed/) does not allow for the prescribing of Armour thyroid. It states:
Liothyronine (including Armour Thyroid and liothyronine combination products) (updated 2023)
Do not initiate.
Deprescribe in patients currently prescribed this medicine.
Prescribe only if no other item or intervention is clinically appropriate.
Prescribe only if no other item or intervention is available.
Prescribe only if for a named indication in this guidance.
The NHS England guidance, Liothyronine – advice for prescribers states:
Products not recommended for prescribing
The prescribing of unlicensed liothyronine and thyroid extract products (e.g. Armour thyroid and ERFA Thyroid) is not recommended as the safety, quality and efficacy of these products cannot be assured:
compounded thyroid hormones
iodine containing preparations
dietary supplementation.
As you can see, it will be very difficult to obtain an NHS prescription for NDT. Many private doctors are willing to prescribe NDT because they have seen their patients improve on this.
If taking levothyroxine plus liothyronine does not work for you, consider NDT but realise that you will have to fight for it.
If you want to have a trial of NDT, do inform your GP so that he can be kept informed of your journey. If you still have symptoms on levothyroxine or levothyroxine and T3, start to keep a diary of your symptoms and test results.
It might be beneficial if you can show that you have been taking it via a private endocrinologist and how it has helped you improve your symptoms.
We suggest you try to find out if there are any NHS endocrinologists that do prescribe this for some of their patients. You can telephone the secretaries of endocrinologists and ask them which endocrinologists do prescribe. If you find one that does, ask for a referral to them if your GP will agree to do this.
If you do get a referral, ask for a trial of, say, 6 months to see if NDT alleviates your symptoms. If it does, then your endocrinologist may then request the GP to take over the prescribing. Unfortunately, the GP does not have to do this and also the local Integrated Care Board (ICB) may not want to pay for this (NDT is very expensive).
You need to explain how much the NDT has improved your symptoms which means that there will be less visits to the GP/hospital and therefore it is costing the GP/hospital/ICB less money for referrals to specialists (often specialists other than endocrinology) plus the cost of other medications.
Some doctors worry about the safety of NDT so you need to let them know that there is no research that we know of that shows it is unsafe. The endocrinologist who gave you the trial may be able to confirm this to your GP.
Sometimes, private endocrinologists also work on the NHS. We have a list of both private and NHS endocrinologists although most of them only prescribe T3.
NDT comes in grains. Generally, 1 grain is 60mg and contains 38mcg of T4 and 9mcg of T3. Some brands have 65mg. Equivalence charts show that 1 grain of NDT has the approximate equivalence of taking 100mg of levothyroxine. Ensure that you discuss dosages with your clinician.
You may be told by your clinician that the amounts of hormone in these branded products are unstable. This is incorrect. The USP of NDT has a similar rule to that of levothyroxine and liothyronine, which means that each NDT tablet must contain between 90% – 110% of the labelled amounts of T4 and T3.
We know that there is a group of people who find that they don’t become well unless they are treated with NDT so if you do not resolve all of your symptoms on levothyroxine, this may be an option for you if you can get it prescribed.
There are no available instructions in the patient information leaflets about how to take NDT. It is assumed that it should be taken on an empty stomach with water.
The food and drugs that can cause problems when taking natural desiccated thyroid are assumed to be the same as those for taking levothyroxine.
For more support check out our online community:
http://www.healthunlocked.com/thyroiduk
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)
Natural Desiccated Thyroid (NDT) – A thyroid medication containing both T4 and T3 prepared from the desiccated thyroid tissue of pigs
Thyroxine – the main hormone secreted into the bloodstream by the thyroid gland. It is the inactive form
Date updated: 17.7.25 (V1.5)
Review date: 17.07.2
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