I have original Medicare (Parts A and B). Do I also have to enroll separately in Medicare Part D prescription drug coverage?

Part D drug coverage is a voluntary benefit; you are not obliged to sign up. You may not need it anyway if you have drug coverage from elsewhere that is “creditable” — meaning Medicare considers it to be the same or better value than Part D. This coverage could come from an employer or union, retiree benefits, COBRA or the Veterans Affairs health program — all of which have an obligation to tell you whether it is creditable. But without such coverage, you need to sign up with a stand-alone Part D drug plan if you want Medicare to help pay for your medications and avoid late penalties. 

Stand-alone Part D plans, which are run by private insurance companies but regulated by Medicare, are plans that provide only drug coverage. Therefore they are for people enrolled in the original Medicare program, which doesn’t cover outpatient drugs. (Only Medicare Advantage health care plans, such as HMOs and PPOs, include Part D drug coverage in a single benefits package.)

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You are eligible for Part D coverage if you are enrolled in either Part A or Part B (or both). To join a stand-alone Part D drug plan, you need to select one plan from many available in your area, and pay a separate monthly premium (in addition to the premium you pay for Part B benefits). The costs of coverage — premiums, deductibles and copays — vary according to the drug plan you choose.  

It’s important to understand that Part D is insurance. Just like any other kind of insurance, you buy it so that you can access it when and if you need it in the future. But, also like other insurance, you can’t postpone enrollment until you suddenly find you need help paying for drugs to treat a medical condition or injury.  You can sign up with a Part D drug plan only during designated enrollment periods. (These periods are explained in detail in the Q&A headed “When can I join a Medicare Part D prescription drug plan?”) 

For information on how Part D drug coverage works, see AARP’s consumer guide to the program at http://www.aarp.org/health/medicare-insurance/medicare_partD_guide/ .