You may switch Medicare Advantage and Part D plans every year during the annual Medicare Open Enrollment period (October 15 through December 7), and, if you are enrolled in a Medicare Advantage plan, you can also switch during the Medicare Advantage Open Enrollment period (January 1 through March 31). It is generally a good idea to compare your plan options every year, even if you are happy with your current coverage, since plans often make changes to their benefits, cost sharing, premiums, and/or provider networks from one year to the next. In addition, you may find another plan that meets your needs better than your current plan if your health needs have changed during the year.