If you have both Medicare and Medicaid, you will be automatically enrolled in a Medicare drug plan. You will get a letter telling you which plan Medicare chose for you. You should check with your Indian health provider or call Medicare (1-800-633-4227) to make sure that your Indian health provider participates in your Medicare drug plan. If it doesn't, you should choose another plan.
Prescription drug coverage from an Indian Health Service, Tribe, Tribal Organization, or an Urban Indian Health Program (I/T/U) is at least as good as the Medicare standard drug coverage (creditable drug coverage). Your Indian health provider will provide you with a notice telling you that your coverage is as good as Medicare's. If you decide to join a Medicare drug plan after you are first eligible, save this notice and show it to your plan to avoid a late enrollment penalty. You must join during a valid enrollment period.
If you have any questions or need help choosing a plan, please contact your local Indian health provider.
(Source: U.S. Department of Health & Human Services)