Medicare Part D covers prescription drugs. Medicare offers prescription drug coverage to everyone with Medicare through private insurance companies. Even if you don't take many prescriptions now, you should consider joining a plan when you first become eligible. If you decide not to join a Medicare drug plan when you're first eligible, and you don't have other creditable prescription drug coverage, you'll likely pay a late enrollment penalty when you join later. Generally, you'll keep paying this penalty for as long as you have coverage.