Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI) are programs managed by the Federal government’s Social Security Administration. Both programs provide money benefits and medical insurance eligibility for many disabled people who meet certain rules. The medical rules (rules establishing whether or not you are disabled) are the same for both programs. Some people will qualify for only one program while others will qualify for both.
Social Security Disability Insurance (SSDI) eligibility is based on how long and how much you contributed to the Social Security Retirement and Disability program as you worked, earned money, and paid Social Security and Medicare taxes. The rules for eligibility can be very complex. Social Security Disability Insurance (SSDI) eligibility usually means early MediCare eligibility.
Supplemental Security Income (SSI) is for disabled persons who either do not qualify for Social Security Disability Insurance (SSDI) or who would get a low amount from that program. Supplemental Security Income (SSI) eligibility should also make you eligible for MediCal if you aren’t already.
This is a very simple explanation and there are many more differences between the programs. If you need more detailed answers, please call the Social Security Administration.