Thyroid UK

Is Levothyroxine toxic?

I was diagnosed with Hypothyroidism a year ago and my GP started me on 100 mcg Levothyroxine. My TSH reading went from 14.91 to 0.4 in four weeks but I had terrible shoulder/neck/head pain and felt ill. GP then reduced the dose to 50 mcg which was ok for four months.

Next TSH reading was 6.68 and dose increased to 75 mcg. Was mostly ok for six weeks but then started suffering from Fog Head, dizziness, terrible indigestion, diarrhoea, muscle aches, etc.

Went to see endocrinologist who told me to increase dose to 100 mcg. After this I had terrible palpitations and was feeling worse and worse. TSH reading went down to 2.02 but still felt lousy. Think I have an intolerance to thyroxine. Does anyone else? I have decreased dose to 50 mcg but still have some palpitations, really bad indigestion and tummy pains/diarrhoea and get very hot when I always used to be cold. Would love to stop Thyroxine and try Armour (NCD). Has anyone out there been successful with this?

This is my first post but I am now getting desperate! I am 62 and have never had a problem with my weight or constipation which are two of the main symptoms of Hypothyroidism. Any suggestions or info about coming off thyroxine would be very welcome.... Many thanks. LizT10

10 Replies

If levo were toxic, thousands of people wouldn't be doing very well on it.

It's just that some of us don't get on with is. Come to that, some of us don't get on with NDT. It's all a question of trial and error to find the form that suits you personally.

Having said that, it's possible that your doctor just doesn't know how to treat you. The dose he started you on could have been too high - most people start on 50 mcg. It might have been just too much of a shock for your body. And it sounds as if he is just looking at the TSH, and ignoring the symptoms and FT4. That is a good formula for keeping your patient sick!

And, what is more, nothing is going to work if you have nutritional deficiencies. But doctors know nothing about that.

What I would suggest, before you launch yourself into the unknown of NDT, is to ask your doctor for the following tests :






vit D

vit B12



He might not do them all, but get what you can. That will give you a clearer idea of what is really going on. The rest you could get done in a private test.

Have your test early in the morning - before 9 am - and fast, just drink water. And leave 24 hours between your last dose of levo and the test. If you always follow that routine, then you will get a clearer idea of your progress - or lack of it. If tests are done at different times of the day, you cannot compare them, and that is where so many doctors go wrong.

Don't forget to ask for a copy of your results - it is your legal right under the Data Protection Act - and post them on - with the ranges - and members will be better able to help you.

It really is a good idea to give levo a fair trial before trying something else. a) because it keeps your doctor on-side, and is easy to obtain on the NHS and b) because levo suits the majority of people if they take enough of it, for long enough, and deal with their nutritional deficiencies. If you chop and change and ignore your nutrition, you're very quickly going to find yourself up the creek without a paddle! :)


Thanks for your reply and useful tips.


You're welcome. :)


I just wanted to point out...

Armour Thyroid is a brand name. It may be the only Natural Dessicated Thyroid (NDT) that some doctors and patients have heard about, but it is not the only NDT there is. Armour Thyroid is the most expensive NDT in the world, but price is not a guide to quality in this case.

Thailand sells three different makes of NDT (that I know of), and they are substantially lower in price than Armour. There are also other brands of NDT from the US and Canada.

The moral? If you discuss NDT with your doctor refer to Armour or "prescription dessicated thyroid" or "dessicated thyroid extract", don't refer to NDT or natural dessicated thyroid. Many doctors have never heard of NDT. Those that have think it is some alternative, new-age, useless rubbish.

One doctor has been heard to refer to NDT as "cutting-edge", which is funny. It was invented, discovered, developed (or whatever word you want to choose) in the 1890s when the very first patient was given raw sheep thyroid sandwiches and it eliminated or improved her hypothyroid symptoms. Luckily, it was very quickly discovered that drying the tissue and turning it into pills worked just as well. It was the only effective treatment for hypothyroidism available for decades. Levothyroxine started becoming common as the treatment of choice in about the 1970s.

Sorry, I didn't mean to go into lecturing mode. :D

Welcome to the forum. :)


In answer to your first question, no levothyroxine is not toxic. Many, many hyopthyroid patients do very well on it. However, there is a percentage that do not do well on levothyroxine alone. You will come across many on this forum. Some do better on combined levothyroxine and liothyronine (T4 + T3). Others do better on liothyronine only. Others do better on desiccated thyroid preparations.

Your comment that weight or constipation are two of the main symptoms of Hypothyroidism, may be true for lots of people. But the golden rule here is that we are all different. Just as not everyone does well on the same thyroid medication, so not everyone suffers with the same hypothyroid symptoms.

As mentioned by Humanbean, Armour is not the only brand of desiccated thyroid. To see names and ingredients of other brands that can be obtained, go to this page on the main Thyroid UK website and click on the purple bar that says *Non-UK - Desiccated Thyroid (aka NDT)

A also fully agree with Humanbean's warning not to refer to it as 'NDT' when communicating with medical professionals. The word 'natural' does not go down well with the vast majority of conventional medics, and is likely to engender the 'raises eyebrows, rolls eyes' attitude towards you.

If you are hoping to obtain desiccated thyroid on NHS prescription, you might also find it useful to read the information about Named Patient prescribing here


Many thanks - all v helpful

1 like

I had a very adverse reaction to levo to begin with, like you say here. I think my experience of it was because I'd been so hypo for so long I was running on cortisol and the effects of cortisol are emphasised by thyroid hormones.


Thanks for your reply.


You have just described everyone of my symptoms but add poor memory which is constantly getting me in trouble ! It's like being on a bloody merry go round that never ends without any relief .Think the next step for drug company will be adding something else in levothyroxine to stop us moaning. It wouldn't surprise me


I am not sure if you are replying to my post ten months ago when I posed the question, 'is levothyroxine toxic?' A lot of people were upset by this but I was pretty desperate at that stage having been told to change my dose time and again but still feeling awful. Last September after a month on T 3 only, I persuaded my endocrinologist to let me go on holiday with no medication at all. He agreed and I have taken nothing at all since then. I don't feel 100 percent all the time but I feel a whole lot better than I did when I was taking pills. I am not suggesting this would suit everyone but I am determined to carry on managing my problem by eating a sensible diet, getting plenty of sleep and trying to avoid stress (easier said than done!)

I am otherwise living a normal life, working, running two houses a hundred miles apart plus visiting my 97 year old mother 100 miles in the opposite direction once a month. She is on 150 mcg Levothyroxine a day and thriving on it!

Find out what suits you best and don't be bullied into taking pills which make you feel worse.

Good luck



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