What is "MSM" as used with glucosamine?

Methylsulfonylmethane is a type of sulfur that can be taken to support muscles and tendons, states Drugs.com. MSM is commonly taken in combination with glucosamine and chondroitin to maintain healthy joints and treat osteoarthritis and other joint-related disorders.

MSM occurs naturally, and it is not approved by the Food and Drug Administration, according to Drugs.com. It is important to check with a doctor before beginning a regimen of MSM, as unpleasant side effects or complications may occur. The combination of chondroitin, glucosamine and MSM should not be taken by diabetics, as the glucosamine can cause a rise in glucose levels.