Anyone entitled to Medicare Part A (whether actually enrolled or not) or who is currently enrolled in Medicare Part B may join Medicare Part D to get help paying prescription drug costs. Enrollment is voluntary except for people who also receive benefits from Medicaid (Medi-Cal in California). If you qualify for Medicaid, the government automatically enrolls you in a Medicare Part D plan through which you will receive your prescription drug coverage. For more information about Part D, see Medicare Part D Prescription Drug Coverage: The Basics. For help choosing a Part D plan, see Medicare Part D: Choosing a Prescription Drug Plan.