Most Medicare beneficiaries 65 years or older have insurance that supplements Medicare or that replaces it entirely, generally with a more comprehensive set of benefits than those provided under the traditional Medicare program. Approximately 20% purchase Medigap coverage. Others get additional protection from retiree health benefits, Medicaid, or managed care plans called Medicare Advantage, which are required to provide at least the benefits of the traditional program but usually provide additional benefits. Only approximately 10% of Medicare beneficiaries are without any additional coverage.
Wilensky GR. The Future of Medicare Supplemental Insurance. JAMA Intern Med. 2013;173(18):1669-1670. doi:10.1001/jamainternmed.2013.9947