When the sun's UVB rays hit the skin it produces vitamin D - a hormone that is important for good health generally, but particularly for people with MS - because it dampens overactive immune responses and protects brain cells. This is why maintaining vitamin D levels through sunlight or supplementation is a key part of the Overcoming MS Program

Research has shown that people with MS have lower levels of vitamin D, and also that vitamin D levels are lower during MS relapses.

But in many parts of the world, sunlight is too scarce, or UVB levels are too low, to produce enough vitamin D, so taking supplements is needed.

Watch this short video about vitamin D

MS and vitamin D dosage

The general population aged four and over should have 125 micrograms of vitamin D per day, on days where it is not possible to get enough vitamin D from the sun. One hundred and twenty-five micrograms is equivalent to 5,000 IU.

However this recommended daily intake (RDI) does not take people with MS into consideration. If you are a PwMS you need a higher dose of vitamin D supplement to get the same effect.

If your doctor finds that you have a vitamin D deficiency, then they may recommend that you take a daily vitamin D supplement of 5,000-10,000 IU to get the level of vitamin D in your blood back up to 150-225 nmol/L (60-90ng/mL). The risk of overdosing on vitamin D is rare, and there is a considerable window of safety, with toxic levels only being a concern over 400nmol/L (160ng/ml) in most people.

MS and low vitamin D level

Not only has lack of vitamin D been linked to increased risk of getting MS, but for PwMS vitamin D offers numerous benefits. These include boosting the immune system, lessening the severity and frequency of MS symptoms and lengthening the time it takes to progress from relapsing-remitting multiple sclerosis to the secondary-progressive phase.

A lack of vitamin D is a worldwide problem with health consequences, especially in countries with colder climates and long winters. It is estimated that one billion people worldwide are deficient in vitamin D.

Experts agree that a level of 25-50 nmol/l is insufficient and that less than 25 nmol/l is deficient. 

To counteract this, PwMS must take vitamin D supplements and make sure that they get daily doses of sunshine when possible. You can calculate the amount of sun you need using the UV index. 

The importance of a vitamin D level test

We recommend that people ask for a vitamin D level test immediately upon being diagnosed with MS. This could be through your general practitioner or using an online kit. 

It is not uncommon to have low vitamin D levels, one billion people across the world are vitamin D deficient.

The results of the first test often show that vitamin D levels are low, which may be what brings on the attack. It should be above 150nmol/L (60ng/mL in the USA).

If vitamin D levels are very low, it can be brought up quickly with a one-off megadose of vitamin D3 (e.g. 600,000 IU) followed by regular capsules or sprays. 

Don't be nervous about large doses; research shows they are safe and actually necessary to raise vitamin D levels quickly. You do this by working out how much is in each tablet and taking the required number. Remember it is fat soluble so it is advisable to take it with a meal or your flaxseed oil.

Research includes:  

  • Geography and latitude epidemiology
  • Population studies
  • Animal studies
  • Case-control studies
  • Cohort studies
  • Randomised controlled trials

Further reading


1. Goldberg P, Fleming MC, Picard EH. Multiple sclerosis: decreased relapse rate through dietary supplementation with calcium, magnesium and vitamin D. Med Hypotheses 1986; 21:193-200.

2. Soilu-Hanninen M, Airas L, Mononen I, et al. 25-Hydroxyvitamin D levels in serum at the onset of multiple sclerosis. Mult Scler
2005; 11:266-271

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018438/ 

4. Munger KL, Levin LI, Hollis BW, Howard NS. Serum 25 hydroxy Vit D levels and risk of MS JAMA 2006; 296:2832-2838

5. Munger KL. Zang SM, O’Reilly E, et al Vitamin D intake and incidence of MS. Neurology 2004; 62 (1): 60-65

6. Cortese M, Riise T, Bjornevik K et al; 7ming and use of cod lover oil, a Vitamin D source and MS risk. EnvIMS study. Mul7ple
Sclerosis 2015;21 914): 1856-1864