A Part D plan is voluntary prescription drug coverage offered by private insurers and approved by Medicare.
Medicare Part D plans help pay for your prescription drugs and protect you from high prescription drug costs. If you are eligible for Medicare Parts A or B, you are generally also eligible for Medicare Part D.
You also have the option of enrolling in a Medicare Advantage plan (Part C). Medicare Advantage plans combine the coverage of Medicare Parts A and B with the prescription drug benefits of a Medicare Part D plan. These comprehensive plans are offered by private insurers.