In clinical trials, several studies reported minimal or absence of side effects after 12 weeks of dosing. Reported side effects from these studies included mild gastrointestinal issues, fatigue, and headache, although they did not appear to differ from placebo. A more recent 26-week study on large joint osteoarthritis observed no adverse events or abnormal changes in lab monitoring when taking 6 grams MSM per day. MSM is considered 'Possibly Safe' at therapeutic doses, although further research is still needed to assess its safety for long-term use.