Thyroid UK
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Bit confused about T3

Hello - I've been reading about T3 and keeping it at the back of mind if all else fails but I'm still trying to get my levothyroxine dose right and checking for all the vitamins and minerals to feel better.

My question is this: Why do English doctors not want to prescribe it - is it because people have been mis-using it to lose weight or is it because it is expensive - and if so - WHY is it so expensive here when it seems to be fairly affordable buying it directly from other countries? Sorry to be so dense.....

11 Replies

This situation with doctors is not only here but everywhere. I think it's for several reasons. One is definitely the fact that most of them don't know much about hypothyroidism at all, not to mention how to treat it properly. Second one is they are under influence of Big Pharma (through money of course) and money rules the world.


Levothyroxine is converted to T3.  It used to believed that this would always work but more recent research shows that it doesn't quite work for some people.  Plus there are people who do well on higher doses of T3 medication than would be expected.  Doctors do not understand why this is so.  T4 is safe in the sense that if a little too much is taken the body converts less to T3, a sort of protective mechanism.  T3 has a shorter half-life of 24 to 48 hours which means it has to be taken twice daily and the body have fluctuating levels.  This makes it difficult to monitor with blood tests.  It doesn't matter in practise because although the blood levels fluctuate the cellular response is more stable.

Liothyronine (L-T3) is incredibly expensive in the UK because the pharmaceutical company is ripping off the NHS and our government doesn't care (I've complained directly to Jeremy Hunt).


Dear Sofitel & Jim,

Many thanks for your replies - just jaw-dropping isn't it?

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I don't necessarily agree that T3 has to be taken twice a day. I take mine once. Even though it has a shorter half life and is into the receptor cells quickly, it is then effective for between one and three days.

The cost in the UK is extortionate, as we know, because Mercury Pharma has the only licence. In other countries the brands are less expensive.


Whoops!  'has to be taken twice a day' is overstating the mark.  Taking it two or more times a day enables more steady levels.  However, the large variations we see in serum T3 levels (pharmacokinetics) are not the same as how T3 acts on the DNA in the cells (pharmacodynamics) which is a slower process (several hours).  Think of drinking a glass of water, you may pee half a glass a few hours later.  The elimination half-life is a few hours but the way our body uses water means we are not affected by the short half-life.  (This isn't a perfect analogy because the water doesn't enter the bloodstream in the same way as T3).

In France T3 (Cynomel) is 1% (yes one precent) of the cost of UK liothyronine, EU 2.75 for 30 x 25 mcg see .  Our government just doesn't care about the NHS.


Dr John Lowe, now deceased, took one dose of 150mcg of T3 in the middle of the night so nothing interfered with the uptake and this is his explanation:

January 30, 2002

Question: I’m a physician who has just begun using T3 in my practice. One thing I’m concerned about is the short half-life of T3. Shouldn’t patients divide their daily dose up and take part of it at least twice each day, or instead use sustained-release T3? It seems that this would allow the effects of T3 to continue through the day rather than stop midway or in the evening?

Dr. Lowe: The short time that T3 is in the circulating blood isn’t the limit of its beneficial effects on the body. When T3 binds to T3-receptors on genes, the binding regulates the transcription of mRNAs, and the mRNAs are later translated into proteins. The transcription and translation initiated by the binding of T3 to T3-receptors occur in waves, and these waves far outlast the T3 that started them at the chromosomes. Moreover, the newly synthesized proteins themselves far outlast the transcription and translation. As a result, a single dose of T3 will be long gone from the patient's system before he or she experiences most of the benefits of that dose—a molecular and metabolic yield that may smoothly spread out over one to three days. The "rocky road" ( August 7, 2001


Big pharma are shocking and really do only care about money. Not just with thyroid meds, others too. My brother has schizophrenia and when he is sectioned there are only 3 drugs they give via injection to all patients with a vast array of mental health problems and each one has horrific side effects. In this day and age and with their resources that is disgusting. But of course it's administered to in patients so there is no money in it..


A friend of mine's stepfather invented a cure for something - sorry can't remember what it was as it was 30 years ago - and a Big Pharma company bought the patent from him so that they could suppress it as they had invested so much money in their own inferior 'cure'. I think that is actually evil.....


Totally agree with you, Big Pharma is evil.

Big Pharma doesn't produce cures, it produces customers!


it is the modern trend - one size fits all.

this page explains some of the complications of dosing with T3.


Thanks linlow - I'll read it now!


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