Vitamin D

People in forest

Vitamin D is essential for bone health and immune system regulation and may have a role in multiple sclerosis too.

Regular time in the sunshine could provide enough Vitamin D for good health, but you can also get it from your food or take supplements, particularly in the winter months.

Low levels of vitamin D have been linked with a range of medical conditions. These include osteoporosis, heart disease, diabetes, cancer and multiple sclerosis. Low vitamin D levels have been linked with an increased risk of getting MS, but also with more frequent relapses and increased disability in those with established MS.

Although these links are well established, it is not yet clear whether supplementing is effective. There are several clinical trials ongoing at the moment to see what doses are appropriate and safe. You may wish to discuss this with your MS team in the meantime if you wish to try vitamin D supplements yourself. You can read more about healthy diet in our series on Diet and MS.

Vitamin D and MS Risk

No single cause for MS has been found. In those people who have a genetic predisposition for MS risk, a number of environmental factors are implicated in causing the disease. Low vitamin D is one of these risk factors, which may work alongside viral infection and other triggers to increase your chances of acquiring MS.

Several large studies from around the world have shown evidence of this link. One study compared 15,000 people with MS and 24,000 people without, and found genetically lower vitamin D levels in the people with MS. Two further studies looked at those joining the US Army or Nursing professions, and compared their blood levels of vitamin D with their subsequent chance of getting MS. Those with lower levels of vitamin D were more likely to develop MS.


​Nearer the equator, the sunlight is stronger and less seasonal, meaning that it is easier for your skin to make sufficient vitamin D all year round. Further from the equator, vitamin D levels and sunshine levels are lower and MS rates are higher. There is a higher rate of MS in Scotland compared with England, and in New Zealand compared with Australia.

Birth month

In the UK more people with MS were born in April and May than October and November. The reverse is true in Australia. If you were born after a winter pregnancy, your mother may have had low vitamin D levels. This may have increased your risk of getting MS if you were already genetically susceptible.

Sun exposure

Low levels of sun exposure, especially during childhood, increase the risk of developing MS. In a study of twins, the twin who developed MS was the one who had lower sun exposure as a child. 


MS rates are lower in countries or regions where the diet includes significant amounts of oily fish, a good source of vitamin D. However, this link might be affected by the genetic make-up of these populations.

Although the evidence for a link between vitamin D and MS risk is consistent, it is not clear what this means for treating existing MS. You may have the following questions:

How do I get vitamin D?


For most people, the most important source of vitamin D is through exposure of the skin to sunlight. If you have fair skin, you just need 20-30 minutes of sunlight on your face and forearms 2-3 times a week. This will generate enough vitamin D for you during the summer months in the UK. The sunshine does not have to feel hot, and you don’t need to risk allowing your skin to redden or burn. Excessive sun exposure carries a risk of skin cancer,

If your skin is dark, if you prefer to cover up more of your body or are obese, you will generate less vitamin D. In the UK, the sunlight between October and April is not strong enough to stimulate your skin to make vitamin D. You might need to ensure your diet has sufficient sources at this time of year.


Vitamin D in food occurs in two forms. Vitamin D2 (ergocalciferol) occurs naturally in yeast and some mushrooms (chanterelles and shiitake). Vitamin D3 (cholecalciferol) is found in oily fish, liver and in small amounts in eggs.

D3 is also the form that we make in our skin cells. Some foods have vitamin D added to them. These ‘fortified’ foods include some margarines, breakfast cereals and white flour. Check the label to be sure.

Your body converts both forms of vitamin D to 25-hydroxyvitamin D (25D). If you have a blood test to assess your vitamin D status, it will measure the levels of 25D in your blood.


Vitamin D supplements come as tablets, capsules or drops. Their strength is measured in both micrograms (µg or mcg) and International Units (IU). Look for those that provide vitamin D3 (cholecalciferol) rather than vitamin D2 (ergocalciferol). They tend to produce a higher and more sustained level of 25D in the blood.

1 microgram (µg or mcg) is equivalent to 40 IU of vitamin D2 or D3.

What counts as 'low vitamin D'?

A lack of vitamin D is thought to be common in the general UK population. The government estimates that over a quarter of adults and children have less than 25 nmol/l of vitamin D in their blood. During the winter months, this figure may be higher.

Despite this, most people with low vitamin D levels do not fall ill, and experts do not agree on what constitutes the 'right' level of vitamin D to have for best health. There is quite a range in healthy people and across the year.

Experts do agree that at the lowest levels - falling into the 'deficient' category on the table below - we are at risk from bone disease. This takes the form of rickets in children and ostoporosis and osteomalacia in adults. For MS, there is no specific guidance.

Optimal greater than 75 nmol/l
Sufficient 50-75 nmol/l
Insufficient 25-50 nmol/l
Deficient less than 25 nmol/l


Should I take vitamin D supplements?

The UK Scientific Advisory Committee on Nutrition has recently set recommended dietary intakes for vitamin D for the first time. These can come from your general diet or from supplements.

  • Everyone in the general population aged 4 and over should have 10 micrograms of vitamin D per day, throughout the year. (This includes pregnant and breastfeeding women and population groups at particular risk of low Vitamin D).
  • It is safe for all infants from birth to 1 year old to have 8.5 to 10 micrograms per day.
  • It is safe for children between the ages of 1 and 4 years to have 10 micrograms of Vitamin D a day.

If you qualify for the UK Healthy Start Scheme, then you can get free vitamins for children and pregnant women.

10 micrograms is equivalent to 400IU. These recommended intakes (RNI) are based on the amount needed to maintain bone health. They are not related to MS specifically, and most trials in MS are looking at much higher doses. If you have MS, you may need a higher dose of vitamin D supplement than a person without MS, in order to get the same effect on your 25D blood levels.

What is the highest safest level?

In July 2012, the European Food Safety Authority (EFSA) proposed a Tolerable Upper Intake Level of 4000 IU (100 micrograms) per day for vitamin D in adults and children over 11. This is a maximum amount that most people could take without harm. Several clinical trials of vitamin D are looking at higher levels and have not yet found evidence of harm.

If you are actually found to be deficient in vitamin D, then your doctor may recommend a supplement of 2000-5000 IU. The aim is to get the levels of vitamin D in your blood up to a level of around 40-60 nmol/l, whilst monitoring blood levels of 25D every 3 months.

The risk of overdosing with vitamin D is rare, but can happen. If you are taking a very high level of vitamin D as a supplement, you may be advised to follow a low calcium diet as well. Usually, this involves cutting down on dairy products in order to prevent calcium building up in the body. Vitamin D toxicity and hypercalcaemia can cause kidney damage if left untreated.

Will vitamin D supplements affect my MS?

As a person with established MS, if you have low levels of vitamin D, you may be more prone to relapses and experience faster disease progression. This has been shown in several ways, including measures of disability (EDSS), brain volume and CNS lesions. There are several possible reasons for this link.

  • Having low vitamin D levels could cause your MS to be more active.
  • Having more active MS could cause your vitamin D levels to be lower. For example, you spend less time outdoors when your MS is active.
  • Another unknown factor causes both low vitamin D levels and more active MS, but the two are not directly linked.

Sun exposure has been shown to reduce the severity and progression of MS and also lift depression. This implies that increasing vitamin D intake could also help, but the advice on what we should do about it is mixed. The main issues are how easily the body can access vitamin D, what it actually does in the body, and what doses might have a measurable effect on MS.

A recent systematic review of all the relevant research claimed that there is not enough strong evidence to indicate that vitamin D supplements can protect the brain from deterioration, although it confirmed the value of sunlight. 

The PrevANZ study in Australia and New Zealand reported in 2022 that taking vitamin D supplements (up to 10,000 IU) does not prevent the development of MS in people with a clinically isolated first symptom indicative of MS (CIS). The VIDAMS study in the USA reported that taking high dose vitamin D supplements alongside glatiramer acetate did not affect the risk of relapsing. 

Further research is ongoing. You can discuss the benefit of vitamin D supplements to you with your MS team.

Will vitamin D supplements interact with my other MS treatments?

No studies have yet shown any harmful interactions between vitamin D supplements and DMDs for MS. In fact, adding vitamin D to the treatment regime is associated with positive benefits in several studies. These have all been studying RRMS, and no data is available yet for an effect on those with PPMS.

Adding high doses of vitamin D to the treatment regime of those with RRMS having interferon B injections reduced the number of new lesions over 48 weeks. Another recent trial looked at the difference in MRI outcomes for those taking vitamin D supplements alongside fingolimod. They found less depression, reduced brain volume loss and fewer new and enlarging lesions among those who took vitamin D every day, compared with casual takers and those who never took vitamin D.

Find out more

Dobson R, et al.
The month of birth effect in multiple sclerosis: systematic review, meta-analysis and effect of latitude.
Journal of Neurology Neurosurgery and Psychiatry 2013;84(4):427-32.
Summary (link is external)
Smolders J, et al.
Association of vitamin D metabolite levels with relapse rate and disability in multiple sclerosis.
Multiple Sclerosis Journal 2008;14:1220-1224.
Summary (link is external)
Ascherio A, et al.
Vitamin D as an early predictor of multiple sclerosis activity and progression.
JAMA Neurology. 2014;71(3):306-314.
Full article (link is external)
European Food Safety Authority.
Scientific opinion on the tolerable upper intake level of vitamin D.
EFSA Journal 2012;10(7):2813.
Full article (link is external)
Scientific Advisory Committee on Nutrition
Vitamin D and health report 2016
Full report (link is external)
Harvey NC, et al.
Vitamin D: some perspective please.
BMJ 2012;345:e4695
Summary (link is external)
Pierrot-Deseilligny C.
Clinical implications of a possible role of vitamin D in multiple sclerosis.
Journal of Neurology 2009;256:1468-79.
Summary (link is external)
Munger KL, et al.
Prevention and treatment of MS: studying the effects of vitamin D.
Multiple Sclerosis Journal 2011;17:1405-11.
Full Text Article (PDF, 103KB) (link is external)
Holmøy T, et al.
Vitamin D supplementation and monitoring in multiple sclerosis: who, when and wherefore.
Acta Neurologica Scandinavica 2012;126(Suppl 195):63-9.
Summary (link is external)
Bayes HK et al.
Timing of birth and risk of multiple sclerosis in the Scottish population.
European Neurology 2010;63:36-40.
Summary (link is external)
Staples J, et al.
Low maternal exposure to ultraviolet radiation in pregnancy, month of birth, and risk of multiple sclerosis in offspring: longitudinal analysis.
BMJ 2010;340:c1640.
Summary (link is external)
Shoemaker TJ and Mowry EM
A review of vitamin D supplementation as disease-modifying therapy
Multiple Sclerosis Journal 2018 24(1) 6-11
Summary (link is external)
Shaheen HA et al.
Does vitamin D deficiency predict early conversion of clinically isolated syndrome? A preliminary Egyptian study
International Journal of Neurosciences 2018 1:1-15
Summary (link is external)
Sintzel MB et al.
Vitamin D and Multiple Sclerosis: A comprehensive review
Neurological Therapies 2017 Dec 14
Summary (link is external)
Simpson S Jr et al.
Sun exposure across the life course significantly modulates early multiple sclerosis clinical course
Frontiers in Neurology 2018 1(9) 16
Summary (link is external)
Simpson S Jr et al.
The role of vitamin D in Multiple Sclerosis: Biology and Biochemistry, Epidemiology and Potential Roles in Treatment
Medical Chemistry 2018 14 (2) 129-143
Summary (link is external)
Wang C et al.
Lower 25-Hydroxyvitamin D is associated with higher relapse risk in patients with Relapsing Remitting Multiple Sclerosis
Journal of Nutrition, Health and Aging 2018 22(1) 38-43
Summary (link is external)
Iacopetta K, et al.
Are the protective benefits of vitamin D in neurodegenerative disease dependent on route of administration? A systematic review
Nutritional Neuroscience, 9 Jul 2018
Summary (link is external)
H. Butzkueven, A-L Ponsonby, M. Stein, R. Lucas, D. Mason, S. Broadley, T. Kilpatrick, J. Lechner-Scott, M. Barnett, W. Carroll, J. Andrew, H. Campbell, J. Morahan, K. Dear, B. Taylor
Results from PREVANZ, a phase 2b placebo controlled double blind dose ranging study of vitamin D to prevent progression to definite multiple sclerosis after a high risk clinically isolated syndrome
Multiple Sclerosis Journal 28 3-SUPPL Oct 2022
Sandra D. Cassard Kathryn C. Fitzgerald Peiqing Qian Susan A. Emrich Christina J. Azevedo Andrew D. Goodman g et al.
High-dose vitamin D3 supplementation in relapsing-remitting multiple sclerosis: a randomised clinical trial
Lancet eClinical Medicine VOLUME 59, 101957, MAY 2023
full text (link is external)
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