Medicare is a nationwide health insurance program that nearly all residents who are at least 65 years old qualify for. In addition to retired and elderly residents, those who have end-stage renal disease (ESRD), amyotrophic lateral sclerosis (ALS) or another qualifying disability may also be eligible for SSI benefits and Medicare health insurance coverage.

What’s more, if you’re eligible for Social Security Disability Insurance (SSDI), you automatically qualify for Medicare coverage. Another qualifying factor is that you must collect SSDI payments over a set period of time before you can enroll. Typically, you must wait the first 24 monthly of collecting SSDI benefits before you enroll. This is known as the waiting period. During your 25th month of receiving SSDI benefits, your SSI office automatically signs you up for Medicare.

It’s important to note that the 24-month waiting period does not apply in all cases. If you have ESRD, your waiting period is much shorter; you can enroll after three months of dialysis treatment. If you have ALS and you can enroll during the very first month that you collect SSDI.

After you pass your applicable waiting period, your SSI office will automatically enroll you in the Original Medicare plan. However, you can request a Medicare Advantage Plan from a private insurance provider. There are four parts of Medicare coverage, and this information can help you determine which plan you need, qualify for and can afford:

Medicare Part A is meant for inpatient care in hospitals, skilled nursing facilities, hospice and home health care. You don’t have to pay any premiums for this Medicare plan if you have worked and paid income taxes for at least 10 years.

Medicare Part B covers outpatient care, such as visits to a primary care physician (PCP) for an annual visit and some medical equipment. Medicare Part A and B combined is what makes up the Original Medicare plan.

Medicare Part C combines Parts A and B, and in some cases includes coverage for prescriptions, dental visits and vision care. These plans are also known as Medicare Advantage Plans, and they are sponsored and managed by private insurance providers. These plans cover what’s included in Original Medicare and more.

Medicare Part D only covers prescription drugs. Typically, you can add Part D to the Original Medicare plan to get comprehensive coverage that’s not sponsored and managed by a private insurance provider.

The type of plan you choose determines your coverage and the cost of premiums, if applicable. In many cases, any applicable Medicare premiums come out of your SSI benefits payment automatically, so you don’t have to worry about paying them.

You can have any Medicare coverage plan as long as your condition meets the SSA’s regulations for coverage qualification. There are many cases where you can also return to work and keep your coverage for up to 8.5 years, even if your SSDI benefits are terminated.

In addition, you can also get Medicare as secondary insurance coverage if you already have health insurance through your employer. Medicare will act as the second payer, handing costs leftover after your employer-sponsored health insurance coverage kicks in.