Medicare Part D helps cover the cost of prescription drugs and is offered through private insurance companies approved by Medicare. It’s designed to work alongside Original Medicare (Parts A and B) or as part of a Medicare Advantage plan that includes drug coverage. Part D plans vary in terms of premiums, drug formularies (the list of covered medications), and pharmacy networks, but all must meet certain minimum coverage standards set by Medicare. These plans help pay for both brand-name and generic medications—from everyday prescriptions to those for managing chronic conditions. Most plans group drugs into tiers, which determine your cost for each medication. While not mandatory, going without Part D when you’re first eligible—and don’t have other credible drug coverage—can result in a permanent late enrollment penalty, even if you sign up later. If you rely on medications or want peace of mind knowing you're protected from high prescription costs, Part D is a critical part of your Medicare coverage.