Most people become eligible for Medicare at age 65, but you can enroll as early as three months before your 65th birthday. In certain circumstances, people under 65 qualify too, sometimes years earlier, through disability benefits or specific medical conditions.
The Standard Enrollment Window at 65
Your Initial Enrollment Period is a seven-month window centered on the month you turn 65. It begins three months before your birthday month, includes your birthday month, and extends three months after it. Signing up during the first three months of that window gives you the earliest possible coverage start date.
If you’re already receiving Social Security or Railroad Retirement benefits, you’ll be automatically enrolled in Medicare Parts A and B a few months before you turn 65. You’ll get a notice in the mail. Part B requires a monthly premium ($202.90 in 2026), so you can opt out if you prefer. If you’re not yet collecting benefits, you need to sign up yourself, and the Social Security Administration recommends contacting them about three months before your 65th birthday.
Qualifying Before 65 Through Disability
If you receive Social Security Disability Insurance (SSDI), you become eligible for Medicare after 24 months of receiving disability benefits. That’s a full two-year waiting period from the date your benefits begin, regardless of your age. Once those 24 months pass, enrollment is automatic.
The waiting period doesn’t always reset from zero if you’ve had a previous period of disability. Months from an earlier disability can count toward the 24-month requirement if your new disability begins within 60 months of when your previous benefits ended. For disabled widows, widowers, or adults who became disabled in childhood, that lookback window stretches to 84 months. And if your current condition is the same as or directly related to a previous disability, there’s no time limit at all on counting prior months.
Railroad workers face a slightly different timeline. Those receiving benefits based on an occupational disability become eligible for Medicare starting in the 30th month after their disability freeze date or, if later, the 25th month after monthly benefits began.
ALS: No Waiting Period
People diagnosed with ALS (Lou Gehrig’s disease) are the major exception to the 24-month waiting rule. Federal law eliminated both the usual disability waiting period and the Medicare waiting period for ALS patients. If you’re approved for disability benefits based on an ALS diagnosis, Medicare coverage begins the same month your disability benefits start. There is no waiting period at all for claims approved after July 2020. This exception applies only to ALS itself, not to other related motor neuron diseases.
End-Stage Renal Disease
Kidney failure that requires regular dialysis or a transplant qualifies you for Medicare at any age, though the timeline depends on your treatment path.
If you’re on dialysis, coverage typically starts on the first day of the fourth month of treatments. You can get coverage sooner, starting from the first month of dialysis, if you participate in a home dialysis training program at a Medicare-certified facility during those initial three months and your doctor expects you to complete training and dialyze at home.
If you’re getting a kidney transplant, coverage can begin the month you’re admitted to a Medicare-certified hospital for the transplant, as long as the surgery happens that month or within the next two months. If your transplant is delayed beyond that, coverage can start two months before the actual transplant date.
What Happens If You Miss Your Window
Missing your Initial Enrollment Period at 65 carries financial consequences that last for years. For Part B, your monthly premium increases by 10% for every full year you were eligible but didn’t sign up. That penalty is permanent, added to your premium for as long as you have Part B. For Part A (if you have to pay a premium because you don’t have enough work credits), the penalty is a 10% increase lasting twice the number of years you went without signing up. Part D carries its own penalty: an extra 1% of the base premium for every month you went without creditable drug coverage, which adds up to 12% per year.
There are two safety valves. A General Enrollment Period runs from January 1 through March 31 each year, with coverage starting the following month. And if you delayed Medicare because you had group health coverage through your own or a spouse’s current employer, a Special Enrollment Period lets you sign up penalty-free anytime while that coverage is active, plus eight months after the employment or coverage ends.
Help Paying for Early Enrollment
If you qualify for Medicare before 65 through disability or kidney failure, premiums can be a burden when you’re not yet at retirement age. Medicare Savings Programs, run by individual states, can cover some or all of your Medicare costs depending on your income.
- Qualified Medicare Beneficiary (QMB): Covers Part A and B premiums, deductibles, and copays. Income limit is $1,350 per month for individuals or $1,824 for couples in 2026.
- Specified Low-Income Medicare Beneficiary (SLMB): Covers the Part B premium. Income limit is $1,616 per month for individuals or $2,184 for couples.
- Qualifying Individual (QI): Also covers the Part B premium at a slightly higher income threshold of $1,816 per month for individuals or $2,455 for couples.
- Qualified Disabled and Working Individual (QDWI): For people with disabilities who are working, with income up to $5,405 per month for individuals.
Resource limits for most of these programs are $9,950 for individuals and $14,910 for couples. Limits run slightly higher in Alaska and Hawaii, and some states use more generous thresholds than the federal minimums.