Usually you must wait until you reach 65 to get Medicare. But there are some exceptions. You can become eligible for Medicare at any age before 65 under the following circumstances:You have a severe illness, injury or disability that prevents you from earning more than a certain amount of money each month and you’ve received Social Security disability benefits for a total of at least 24 months — which don’t have to be consecutive.You have Lou Gehrig’s disease (amyotrophic lateral sclerosis, or ALS). You qualify for Medicare the month you become entitled to Social Security disability benefits. In other words, you don’t have to wait until you’ve been receiving them for 24 months.You have permanent kidney failure (usually called end-stage renal disease, or ESRD, and defined as requiring a kidney transplant or regular dialysis) and you or your spouse has paid Social Security payroll taxes for a certain length of time. This period varies according to your age.