Medicare Plan G is one type of Medicare Supplement Plan, also called Medigap Plans. Medigap plans are designed to help pay some of the hospital and medical costs not covered by Original Medicare, Parts A and B and are sold by private insurance companies. Generally, you have to be enrolled in Medicare Parts A and B to buy a Medigap plan and continue to pay your Part B Premium.
There are 10 Medigap plans available in every state (with the exception of Massachusetts, Minnesota and Wisconsin), denoted with a letter A, B, C, D, F, G, K, L, M and N. The benefits of each Medigap plan type are standardized across the country although prices may vary across different insurers.