I have been on Fosamax for 10 or 11 months now, once a week, with no side effects. I follow the directions explicitly. \Although it will not strengthen the bones, it supposedly keeps them from getting worse. My neighbor was on it for five years with no side effects, but she is on the five-year break from it now. A rheumatologist suggested Evenity for me because she said I could not take any other bone-strengtheners after having radiation for cancer (many years ago). Evenity was disapproved by the FDA until finally being approved last April. Its possible side effects include stroke and heart attack. Not my choice! Good luck to you. God bless.