If an individual is receiving Supplemental Security Income (SSI) disability, they are not qualified to receive Medicare insurance coverage until they reach the age of sixty-five years old. (Instead, they are eligible for Medicaid.)
However, upon turning 65, SSI recipients can receive Medicare based upon age. How? By filing an "uninsured Medicare claim." The SSI program actually requires SSI beneficiaries to file uninsured Medicare claims, so that some of the Medicaid burden will be taken off of states. It is cheaper for states to pay the Medicare premiums for their Medicaid recipients rather than to continue paying for all of their medical expenses through Medicaid, so that Medicare will become a primary payer and Medicaid will become a secondary payer.
If you receive SSDI, you will have to pay for Medicare premiums in most cases. The fact you were approved for SSDI makes you eligible for Medicare earlier than you otherwise would be (at age 65), but it doesn't pay your premiums.
However, individuals who receive SSDI and aren't eligible for SSI disability can nevertheless receive help from their states in paying for Medicare premiums. These individuals should check with their local social service offices to determine if they might be entitled to help for paying their Medicare premiums. The programs that help pay Medicare premiums are called Medicare Savings Programs. You can read more about them in Nolo's article on Medicare Savings Programs.
Learn more about the Medicare and Medicaid that comes with disability benefits.