Supplementation recommendations are between 1-3 grams taken twice daily.
MSM is extremely safe. Extensive toxicology data shows that it can be taken in high doses for a long period of time. Supplementation recommendations are between 1-3 grams taken twice daily.
Clinical trials have investigated doses ranging from 1,500 mg per day up to 6,000 mg per day. Stanley Jacob, MD reports using MSM in his patients at doses of up to 100 grams per day with no ill effects under highly controlled medical treatment regimens in a hospital clinic (MSM: The Definitive Guide).
MSM toxicity studies indicate that these large doses do not present safety issues, however it is possible that they could result in occasional loose stools or other minor effects.