Any U.S. citizen or legal resident aged 65 or older is potentially eligible for Medicare, provided their income and the value of their assets are not too high. Citizens and legal residents under the age of 65 may be eligible if they are on SSDI or have certain medical conditions.
Citizens and applicants with resident visas who have lived in the U.S. for five years in a row and who have been receiving SSDI for at least 24 months are eligible for Medicare. People in this situation do not need to apply and should automatically be enrolled and receive their Medicare card three months before they become eligible.
It is also possible to be eligible for Medicare before age 65 with a diagnosis of end-stage renal disease. Applicants must have either had a kidney transplant or be receiving dialysis treatments. They must also be eligible to receive SSDI or railroad retirement benefits or otherwise be considered fully insured by Social Security.
A diagnosis of amyotrophic lateral sclerosis, better known as Lou Gehrig's disease, also makes applicants under the age of 65 eligible. Once SSDI has been established for the condition, enrollment in Medicare is automatic and immediate. It is also automatic for railroad workers receiving a disability check for the condition.