Vitamin D Supplementation in Multiple Sclerosis

Scientific evidence suggests a link between vitamin D deficiency and multiple sclerosis (MS). In fact, vitamin D deficiency may be a risk factor for MS and may increase the risk of MS exacerbations. Given this, if you have this disease, it's worth discussing with your doctor whether or not you need vitamin D supplementation—and how much to take.

Your doctor may or may not recommend a prescription supplement, but be aware that even over-the-counter options may interact with medications (and other vitamins) and also need to be taken at certain times of the day to be most effective.


What Does Vitamin D Have to Do With MS?

MS Risk and Vitamin D Deficiency

MS is much more prevalent in northern latitudes, where the weather is colder and the sunlight is less intense. Vitamin D is believed to play a role in this trend; in addition to dietary sources of the vitamin, the sun's ultraviolet rays help your body produce vitamin D.

It's thought that this contributes to the higher prevalence of MS in the Midwest and Northeast regions of the U.S., as seen below.

In addition, people who have MS tend to have lower levels of vitamin D than counterparts who do not have the condition. The reason for this association isn't clear, but researchers have been investigating.

While it is a good idea for everyone to maintain a balanced diet, vitamin D deficiency is a common problem that many people don't know they have.

If you have a known risk of MS, such as a family history of the condition or if you have an autoimmune disease, it makes sense to pay special attention to getting enough vitamin D.

MS Progression and Vitamin D Deficiency

Vitamin D may also play a role in how the MS disease course progresses; some research suggests that relapses are associated with low levels of vitamin D.

However, there is mixed evidence regarding whether supplementation could improve MS symptoms, exacerbations, or disease progression. While some studies note a potential role for supplementation in this regard, others have not found any impact on MS at all.

In addition to the symptoms that occur with relapses, some conditions that are more common among those with MS—osteoporosis and depression, for example—are worsened by vitamin D deficiency. Both of these have been proven to improve with vitamin D supplementation.

Target Level and Supplementation for MS Patients

The research supporting an actual benefit with vitamin D supplementation in MS is scarce, although there are a number of ongoing trials. To date, there is currently no standard guideline stating exactly what a normal or target vitamin D level is for a person with MS. Likewise, there is no protocol regarding checking vitamin D levels.

Getting some sunlight on a regular basis will help. As little as 10 to 15 minutes of walking or sitting in moderate sunlight a few times per week can provide most people with enough vitamin D.

Many foods are natural sources of vitamin D (though few have significant amounts), and others, such as milk and dairy products, are fortified with vitamin D.

You can talk to your doctor about whether you are getting enough vitamin D from your diet and from sunlight, or whether you also need to also use an over-the-counter or prescription supplement.


If your doctor does recommend vitamin D supplementation, your dose may be based on your vitamin D level, where you live, and the time of year; you may need more vitamin D during months when there is less sunlight.

While not a hard-and-fast rule, a typical adult vitamin D dose is between 800 and 2,000 international units (IU) of vitamin D daily. Some doctors may recommend a maximum daily dose of 4,000 IU.

However, if your vitamin D level is very low to start, your doctor may prescribe a higher dose at first and then lower it (e.g., 50,000 IU weekly for six to eight weeks, then 2,000 IU daily thereafter).

Dosing is highly variable and is individually tailored. Vitamin D absorption is best if taken in the morning and with food.

Effects of Excessive Vitamin D

Vitamin D is generally safe, but it can cause side effects if taken in excessively large doses. Vitamin D toxicity does not worsen MS itself, but some of these side effects may compound your already existing MS symptoms.

The main consequence of vitamin D toxicity include:

  • Nausea and/or vomiting
  • Irritability and/or confusion
  • Constipation
  • Fatigue
  • Decreased appetite
  • Weakness
  • Kidney stones

The treatment for vitamin D toxicity is usually discontinuation of vitamin D supplements. If your calcium level is high, you may need other medical interventions to bring down the calcium levels in your blood.

A Word From Verywell

The interaction between vitamin D and MS has gained a great deal of attention, but the ideal vitamin D level and recommended dose in MS is not totally clear. As with other vitamins and supplements, it's best to discuss supplements with your doctor, even if you plan to take an over-the-counter form.

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