Understanding Who Can Purchase Medicare Supplemental (Medigap) Coverage

Medigap policies fill gaps in Original Medicare, but eligibility depends on enrollment in Parts A and B, age, timing and whether you’re in a Medicare Advantage plan.

Medicare supplemental insurance, known as Medigap, is intended to cover out-of-pocket expenses that Original Medicare leaves uncovered, but it is only available to individuals who hold both Part A (hospital) and Part B (medical) coverage. The policy cannot be paired with a Medicare Advantage plan, which replaces Original Medicare’s benefits. Federal law grants a six-month Medigap Open Enrollment Period starting the first month a person turns 65 and enrolls in Part B; during this time insurers cannot refuse coverage or charge higher rates based on health status.

Once the open enrollment ends, insurers may use medical underwriting, leading to higher premiums or denial of coverage, particularly for those under 65 who qualify for Medicare due to disability or ESRD, where state rules vary. Prospective buyers should assess their expected medical usage, budget flexibility, and whether they need additional protections such as foreign emergency coverage, while remembering that Medigap does not include routine dental, vision, hearing, long-term care, or prescription drug coverage, which requires a separate Part D plan. Comparing standardized plans before the enrollment window closes can help secure the most favorable terms.