Methylsulfonylmethane (MSM) is a form of sulfur that has been reported to be helpful for some people with fibromyalgia. It can take as much as 12 to 15 grams a day (12,000 to 15,000 milligrams, or 24-30 capsules) to see the benefit. Start with 6 grams a day in the beginning, as it is best to always use the lowest dose possible of any supplement. If MSM helps within three to four weeks, then you can reduce the dose to the lowest dose that maintains the benefit. Taking it with vitamin C probably helps the absorption of the MSM.