Medicare drug plans can differ in ways that can have a big impact on your out-of-pocket costs, including monthly premiums, the list of drugs covered by each plan, how much the plan charges for preferred and non-preferred drugs, and how much the plan charges for high-cost specialty drugs. Not everyone will save money by switching plans, but it generally makes sense for everyone to compare their plan options each year to see if there is a less expensive option for the coverage you need.