You may have seen an article from ACTRIMS (Americas Committee for Treatment and Research in Multiple Sclerosis) with the headline Vitamin D at High Dose Can Worsen MS, Early Study Says. We’ve written a short blog to provide a little more background and context to the study, and to hopefully reassure you that you don’t need to ditch the vitamin D!

vitamin D

You may have seen some research presented at the ACTRIMS (Americas Committee for Treatment and Research in Multiple Sclerosis) written up with the headline Vitamin D at High Dose Can Worsen MS, Early Study Says. We’ve written a short blog to give a short summary and try to alleviate any worries you might have. 

The first thing to consider is that it was a study with mice, not in humans. We know through the HOLISM and other studies in humans that people with MS have a better quality of life and fewer relapses when taking vitamin D supplements.

What is a high dose? 

In this study, they were extremely high doses for mice, and we don’t know what the conversion rate from mice to human super high dose would be, so it isn’t necessarily ‘like for like’ values to begin with. Toxic levels of vitamin D generally only become a concern over levels of 400nmol/L (160ng/ml) in the vast majority of people.  In those with chronic kidney disease or conditions such as sarcoidosis and hyperparathyroidism, there is more potential for vitamin D toxicity, so vitamin D levels need to be monitored more closely, and doses adjusted on an individual basis.

Additional points to think about  

What happens? 

It isn’t vitamin D per se that causes problems, but rather the resulting high levels of blood calcium (hypercalcaemia).  We know that in terms of calcium levels, that humans need have vitamin D3 levels of > 400 nmol/L to induce hypercalcaemia. In this study, the high levels of vitamin D and high levels of calcium worsened myelin loss and disability in an animal model of MS (EAE).   

Those in the moderate dose group had a benefit in terms of MS activity (this is where OMS advise people to be).  It is this dose that more closely resembles the OMS recommendations, and is therefore reassuring both in terms of lack of harm, and potential benefit. 

Should I worry about the recommendations from OMS? 

OMS recommends getting your vitamin D from the sun, when possible, or to take 10,000 IU of vitamin D3 daily in winter / 5,000 IU in summer.  On exposure to strong sunlight the body naturally makes 15,000IU daily, and never gets hypercalcaemic, therefore our recommendations are perfectly sensible

We recommend that you keep your vitamin D level at 150nmol/L – 225nmol/L (60 – 90 ng/mL in the USA). If your doctor finds that you have a vitamin D deficiency, then they may recommend that you take a higher dose supplement for a short period of time, or a single mega-dose (e.g. 600,000 IU) to increase your level rapidly.

If you are very concerned, you could ask your GP to check your calcium levels to seek reassurance.

There is a wealth of information and studies about vitamin D on our website. 

High Dose Vitamin D 

The Coimbra Protocol is a high-dose treatment of MS (starting at 1,000 per kg body weight per day). This is much higher than the OMS recommendations. We recently published an article about this on our website. While receiving treatment via the Coimbra Protocol, you need to follow strict dietary restrictions to avoid hypercalcemia. The treatment has to be given by a medical professional who has been trained in the Coimbra Protocol.

Written by Lucy Noble, edited by Dr. Jonathan White


Darius Häusler, Sebastian Torke, Evelyn Peelen, Thomas Bertsch, Marija Djukic, Roland Nau, Catherine Larochelle, Scott S Zamvil, Wolfgang Brück, Martin S Weber, High dose vitamin D exacerbates central nervous system autoimmunity by raising T-cell excitatory calcium, Brain, Volume 142, Issue 9, September 2019, Pages 2737–2755,

You can read more about vitamin D here. 

Vitamin D
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Graham Anderson (not verified)

Thank you so much Lucy as your explanation is very clear and has allayed the concerns that I had when previously reading other papers.


[~Wallinda] -Hello - I don't believe these people are 'bots' as you say, we ensure to check comments before posting (unless someone is signed in ot their OMS account).

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??????Mrs. Loren Bishop-Brown (not verified)

This proved valuable! Thank you

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Muhawala (not verified)

Thank you. That really puts things in perspective.

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Kris (not verified)

I, too, was very concerned about my Vitamin D regimen. Thank you for breaking this down for the average Joe (or Jane☺️). I feel so much better.

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Mike (not verified)

Thank you for this article!

This past January when I had my annual physical, I asked my PCP to include a vitamin D along with other bloodwork. The result was 74 ng/mL. According to my PCP, that is "very good." That's because the measurements that he's using states that anything between 30-100 is optimal. 30 is optimal??!!

I've been taking 10,000 IU/day ever since being diagnosed (2015), and every time that my vitamin D level has been measured, it's usually around 75, sometimes a little higher. Since OMS says that the optimal level is between 150-225, should I increase my vitamin D supplement intake?

Of course, if I actually get my vitamin D level up to the OMS recommended level, my PCP might be alarmed, since, according to his measurement, anything over 150 might be toxic! Maybe I should have him read your article...


Hi Mike - I passed your comment onto our medical advisor, who has responded with the following:

Many thanks for getting in touch. There is no need for alarm here, your vitamin D levels are perfect!!

I see that you report your level in ng/ml (which is the standard unit in the U.S.A.). The 150-225 you refer to is in nmol/L, the unit used in Europe and almost everywhere outside of the United States (just to be confusing!!).

The OMS recommended vitamin D level is 150-225 nmol/L, OR 60-90ng/ml, so your levels are exactly where we would want them to be, coming into the summer time, and your dosing regimen seems to be completely appropriate.

I hope this clears things up for you.

Take care and best wishes,


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Dmitriy (not verified)

Mike, thanks for the comment!
Tell me, have you been taking vitamin D regularly since 2015?
When was the last time you had an exacerbation of the disease?

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Raquel (not verified)

Maybe you need to add vitamin k2 supplements to your vitamin d regime as it helps absorption!

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Maria L. (not verified)

I wonder what `5000 iu' in summer actually means - is it the 3 official summer months? when should i switch? i think i want to avoid checking my levels every few months

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