Thyroid UK
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Changing to NDT

Hello everyone - I am intending to make the switch from levo to NDT soon. I have two questions and would be grateful if anyone can give me any advice. Firstly, would it be sensible to get some tests done before I switch, so that I can tell if the NDT makes any difference? In March last year I was found to be deficient in Vit D, and wonder if I should make sure this is OK before making the switch.

And secondly, what is the best way of making the switch? I am on 225mcg of levo. Some people seem to advocate just switching to an equivalent amount of NDT, and other advice says to take it slower.

14 Replies


225mcg Levothyroxine is roughly equivalent to 3.5 grains NDT. As there is 31.5mcg T3 in 3.5 grains it is better to titrate dose to see how well you tolerate T3. I would reduce Levothyroxine by 75mcg and introduce 1 grain NDT every 2-4 weeks until you are taking 3.5 grains. Hold at 3.5 grains for 6-8 weeks and have a thyroid function test including FT3 before increasing further.


Thanks, that's helpful. The only difficulty is that I have levo tablets in 100s and 25s only. Do you think it would be OK to reduce by 100mcg while upping the dose of NDT?



Cut the 100mcg in half to 50mcg + 25mcg.


Oh yes - I completely forgot that you could do that. Thanks!


Repton1 You need to ensure that all your vitamins and minerals are optimal so that thyroid hormone has the best chance of working properly.

As you knew last March that your Vit D was deficient, did you start supplementing? When supplementing you need to retest once or twice a year to ensure you stay at the recommended level of 100-150nmol/L.

And what about B12, Folate and Ferritin which you said were 'OK'. What were the actual figures? Optimal levels are:

B12 - very top of range, even 900-1000

Folate - at least half way through it's range

Ferritin - half way through it's range, with a minimum of 70 for thyroid hormone to work properly.

And as you have Hashi's, have you adopted a strict gluten free diet and are you supplementing with selenium, both of which are supposed to help reduce antibodies.

Definitely get new thyroid tests done, you need a base line so you can follow your progress. It might be an idea to do a Blue Horizon Thyroid Plus Eleven to re-test all your vitamins and minerals at the same time.


Thanks for your reply. Ferritin was 56 (range 13 - 150), folate was 691 (range 285.4 - 1474.7), B12 was 130 (range 25.1 - 165.0).

I did start supplementing with VitD3 and K2, selenium and occasional magnesium. I did not cut out gluten as I ended up having a blood test for coeliac disease (which came back negative).

I think the Plus Eleven test would be a good idea.

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Even if your coeliac test is negative it's worth trying to go gluten free. Many of us find it helps.

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Hi, just reading your post and Clutter's replies with interest.

Just a thought. I have Coeliac Disease (CD), been diagnosed over 40 years. When I had a blood test it was negative. But because of previous history (long story!) they sent me for endoscopic biopsy which proved instantly that I definitely had CD. So it may be worth pursuing that one further if you still have digestive issues. There are many other symptoms associated with CD which doctors don't take into account.

If you have anaemia, mouth ulcers, very bloated tummy (particularly after wheat etc) fatigue, 'explosive' motions (this is what they used to call it lol) worth getting further investigation done.


Hi, that's very interesting as I was aware that the blood test isn't necessarily definitive re CD. It was considered because I was having unexplained stomach ache, but that seems to have gone away again. I don't really have any of the other symptoms, apart from fatigue.


Repton1 It doesn't matter that your coeliac test was negative. Gluten contains gliadin which is a protein thought to trigger antibody attacks. It's because it can trigger the antibody attacks why you should try a gluten free diet not just because of coeliac disease.

You can see that your ferritin needs to increase. You can either supplement with iron or eat liver regularly (I've had great success raising my ferritin by just eating liver once a week, I don't tolerate iron supplements well).

Folate should be at least 880 (which is half way through the range you quoted. Eating leafy greens helps raise folate, as does supplementing with a B Complex.

Not sure about your B12, there are usually three measurements such as:

<140 = deficient

140-250 = insufficient

> 725 = consider reducing dose.

But as already mentioned the very top of range, even 900-1000 is recommended and that applies if the unit of measurement is pmol/L. Is there any further information about your B12 such as unit of measurement or other ranges?

If you are taking D3 and K2 regularly then you should also take magnesium regularly as it is an important co-factor of D3 -


Take it slowly, sometimes the extra T3 is a shock to the system. To avoid that I would say start on a low dose and build up over a few weeks.


When I switched from 125mg Levo to NDT. I stopped Levo and I started with 1 grain in two halves. One in the morning and the other in the afternoon. After several weeks I was on three grains per day this made me feel bad so I gradually reduced it. I am now on two grains per day and feel great. Everyone is different I weigh 135 lbs and I am 5ft 8 inches tall.

I am sure the weight must come into the amount of NDT?

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I was on 150 levo for 8 years and simply stopped and started on 2 grains NDT the following day. No side effects and many of the rotten feelings disappeared within days. In my case, however, I knew there was nothing basically wrong with my hormonal system, unlike the vast majority of thyroid victims.

It is possible that any "incorrect" blood results could be rectified by simply changing the medication.


Thanks for everyone's replies they have all been very helpful. I am intending to cut gluten out and improve further with supplements. I am currently taking Vit D and Vit K at the same time each day, and selenium and magnesium spaced out later in the day, although I sometimes (often) forget.

I would have replied sooner but yesterday I landed a job for the first time in years and needed some time to process that fact! Now I have the completely unexpected dilemma of whether I should try and make the switch to NDT during the first few weeks of a new job.


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