Medicare Part D is a prescription drug coverage program offered through private insurance companies approved by Medicare. It helps cover the cost of prescription medications, including many generic and brand-name drugs. Part D plans vary by provider, so premiums, formularies, and out-of-pocket costs can differ, but all must meet certain minimum standards set by Medicare. This coverage can be added to Original Medicare, some Medicare Cost Plans, or Medicare Medical Savings Account Plans to help manage prescription expenses and avoid high drug costs.