Medicare Advantage Plans must follow Medicare’s rules
Medicare pays a fixed amount for your care each month to the companies offering Medicare Advantage Plans. These companies must follow rules set by Medicare.
However, each Medicare Advantage Plan can charge different out-of-pocket costs and have different rules for how you get services (like whether you need a referral to see a specialist or if you have to go to only doctors, facilities, or suppliers that belong to the plan for non-emergency or non-urgent care). These rules can change each year.