To be eligible for Medicare before the age of 65, most people with impairments must first qualify for Social Security Disability Insurance, or SSDI. People on SSDI often have a two-year waiting period before they may enroll in Medicare.

Here's everything you need to know about how persons with disabilities can qualify for Medicare, as well as how Medicare works for people under the age of 65.

Qualifying for Medicare based on disability

Before you can be eligible for Medicare based on disability, you must first qualify for SSDI. SSDI eligibility is based on two factors: health and job history. 

After receiving SSDI, you must wait two years before applying for Medicare (unless you qualify for specified exceptions).

Disability requirements for SSDI

SSDI benefits are not available for all impairments or illnesses. The Social Security Administration, or SSA, refers to its own SSDI definition as "strict."

According to the SSA, all of the following must be true in order to qualify for SSDI benefits:

• You are unable to work or engage in other "substantial gainful activity" due to a medical condition.
• Because of the situation, you are unable to perform previous tasks or adjust to new ones.
• Your medical condition has been present for at least one year, is expected to last at least one year, or will result in death.

Work requirements for SSDI

To be eligible for SSDI, you must have a particular level of job experience. You qualify through Social Security work credits, which are calculated in the same way as Social Security retirement payments.

Work can earn you up to four credits each year. In 2023, you gain one credit for every $1,640 in earned wages or self-employment income, for a total of $6,560 for the year.

To qualify for SSDI, most applicants must have 40 Social Security work credits. If you earn all four each year, you'll need ten years of experience. However, at least some of the work must be recent: You must have earned 20 work credits (equivalent to five years of qualified work) within the 10-year period ending the year your impairment began.

If you are under the age of 31, you may be able to qualify for SSDI with fewer recent work credits.

Only Medicare Part A is free

For those receiving SSDI benefits, Medicare Part A is free. Because Part B is theoretically voluntary, you must pay premiums unless you opt out and postpone Part B participation.

If you join up for a Medicare Advantage plan, a Medicare Part D prescription medication plan, or Medicare Supplement Insurance, you will also have to pay premiums.

Medicare disability waiting period

If you are under the age of 65 and receive SSDI, you must normally wait 24 months before being eligible for Medicare.

During that 24-month period, you may be eligible for additional health-care help, such as:

• Medicaid: If you get SSDI or Supplemental Security Income, or SSI, you may be eligible for Medicaid in several states. Because each state manages its own Medicaid program, you must check your state's rules to discover if you qualify.
• Marketplace coverage: In the health insurance marketplace, you can opt for coverage from a private insurance carrier. Depending on your income, you may be eligible for low-cost coverage — but keep in mind that your SSDI income counts toward those restrictions.

People with certain conditions don’t have to wait 24 months

The 24-month waiting period for Medicare does not apply if you have specified ailments.

End-stage renal disease

If you have end-stage renal disease, or ESRD, you can normally acquire Medicare starting on the first day of your fourth month of dialysis treatments if you meet certain Social Security and health-related conditions. You may also be able to qualify for Medicare coverage sooner if you receive home dialysis training.

If you need a kidney transplant, Medicare coverage begins the month you are admitted to a Medicare-certified hospital for the transplant or related services prior to the transplant. This coverage, however, is only available for two months before your transplant. If the transplant is postponed or rescheduled, you are eligible for Medicare coverage beginning two months before the new date.

Lou Gehrig’s disease, or amyotrophic lateral sclerosis

If you receive SSDI benefits because you have Lou Gehrig's disease, or ALS, you are eligible for Medicare the first month you receive your payments.

Signing up for Medicare based on disability

When to sign up for benefits

When you become eligible for Medicare owing to disability, you start an initial enrollment period, just like beneficiaries who qualify based on age. This is the time when you decide what kind of Medicare coverage you want.

The initial enrollment period begins before the end of your 24-month waiting period. It begins in the 22nd month of receiving SSDI benefits and lasts for seven months.

What kinds of Medicare plans are available?

If you qualify for Original Medicare due to a disability, you will receive it automatically. Original Medicare consists of Medicare Parts A (hospital insurance) and B (medical insurance). You are not, however, compelled to remain on Original Medicare.

If you want to add or change one or more of the following choices, you must first sign up:

• Medicare Advantage, also called Medicare Part C, plans.
• Medicare Part D prescription drug plans.
• Medicare Supplement Insurance, or Medigap.

Medicare special needs plans

You may be able to purchase a special needs plan, or SNP, under Medicare Advantage. SNPs provide benefits that are tailored to the individual care needs of distinct groups.

SNPs are classified into three types:

• Chronic Condition SNPs are available to beneficiaries with certain severe chronic conditions.
• Institutional SNPs are accessible to beneficiaries who require the kind of care provided by specified facilities or who will reside in certain facilities for at least 90 days.
• Dual-Eligible SNPs, or D-SNPs, are offered to beneficiaries who are eligible for both Medicare and Medicaid in order to coordinate benefits.

At medicare.gov/plan-compare, you can learn about the different types of plans available in your area, their benefits, and membership criteria.