To qualify for Medicare, one must be at least 65 years of age, a U.S. citizen or permanent legal resident, and be eligible for Social Security or railroad retirement benefits, or have a spouse who is eligible for such benefits, notes AARP. Separate requirements exist for those under age 65.
A person with Lou Gehrig's disease, or amyotrophic lateral sclerosis, automatically qualifies for Medicare no matter his age, according to AARP. Under certain conditions, someone under 65 who receives disability pensions from the Railroad Retirement Board may qualify for Medicare. A person under 65 with permanent kidney failure who has paid Social Security taxes for an extended period of time may qualify for Medicare as well. Individuals who have received Social Security disability benefits for a minimum of two years may also be eligible for Medicare.