Medigap (also called Medicare supplement insurance or Medicare supplemental insurance) refers to various private health insurance plans sold to supplement Medicare in the United States. Medigap insurance provides coverage for many of the co-pays and some of the co-insurance related to Medicare-covered hospital, skilled nursing facility, home health care, ambulance, durable medical equipment, and doctor charges. Medigap's name is derived from the notion that it exists to cover the difference or "gap" between the expenses reimbursed to providers by Medicare Parts A and B for services and the total amount allowed to be charged for those services by the United States Centers for Medicare and Medicaid Services (CMS). Over 14 million Americans had Medicare Supplement insurance in 2018 according to a report by the American Association for Medicare Supplement Insurance. Eligibility Medicare eligibility can start for Americans when they turn at least 64 years & nine months old or upon retirement. Those with a disability, End Stage Renal Disease (ESRD), ALS or on Social Security disability for 24 months in a row may also qualify for early Medicare benefits. A person must be enrolled in both Part A and B of Medicare before they can enroll in a Medigap plan. Upon enrollment, Medicare enrollees become eligible for Medigap Open Enrollment. This period starts on the first day of the month one turns 65 & enrolled in Medicare Part B and lasts for six months. During this period, a person can buy any Medigap plan regardless of their health status (called "Guaranteed Issue Rights"). This is different than if someone is losing group coverage or retiring. When this occurs, the person is eligible to exercise his or her "Guarantee Issue" right. With a Medigap guarantee issue right, a person can buy a Medigap Plan A, B, C, F, K, or L that is sold by any insurance company in their state. In addition, the insurance company cannot deny or raise the premium due to past or current health conditions. Also, the insurance company must cover any pre-existing conditions. Instead of exercising the guarantee issue right, a person can opt to go through the underwriting process in order to buy a plan G or N. Once a person is outside their open enrollment period and or guarantee issue, they can change their Medigap plan, but they will be subject to health underwriting by the insurance company they are applying with. Monthly premiums