Medigap is a “supplemental insurance” policy that is sold and administered by a private company meant to fill the gaps in the coverage provided by Part A and Part B. Most plans will help with Medicare co-payments and with paying for some care not otherwise covered by Medicare. 

Usually, if you decide to drop Medigap you will not be able to get the same policy again. 

You can directly compare Medigap plans by going to medicare.gov. 

Remember the following when considering a Medigap plan:

• Be sure to buy your chosen Medigap plan within six months of getting Medicare Part B. Enrolling during the six-month open enrollment period will mean you are guaranteed to get the policy you want; otherwise the company can charge you more for the same coverage or can turn you down for coverage altogether.
• Make sure to keep your existing insurance coverage until your Medigap policy is in place to make sure you are not excluded from treatment or charged more for any preexisting conditions. If you do not sign up for coverage during the open enrollment period and have not had six months of medical insurance without a 63-day lapse immediately before enrollment, you can be charged more if you have preexisting health problems or they can exclude preexisting condition coverage for up to six months.  
• Medigap plans are labeled A through N and offer varying levels of coverage. Each of the letters stands for a standardized plan so you know that you are getting the same coverage with one company’s plan G as you will get with another company’s plan G. (The types of coverage offered by each plan are detailed in a table at http://www.medicare.gov/supplement-other-insurance/compare-medigap/compare-medigap.html). This does not mean that you will pay the same premium with both companies or that the customer experience will be the same, so be sure to compare insurance providers. The cost will also vary depending on your location and age.
• In 2020, Medicare was no longer allowed to cover the Part B deductible, thus, Medigap Plan F and Plan C have been phased out. If you are enrolled in either of these plans, you will be grandfathered in, however, premiums will be subject to increases. Once prices increase, you may want to revisit your plan. Changes can be made during the open enrollment period between October 15th and December 7th every year. Medigap plans C and F are not available to people who were newly eligible for Medicare on or after January 1, 2020.

Sources: 

• “When Can I Buy Medigap?” www.medicare.gov, www.medicare.gov/supplement-other-insurance/when-can-i-buy-medigap/when-can-i-buy-medigap.html.
• “When Can I Buy Medigap?” www.medicare.gov, www.medicare.gov/supplement-other-insurance/when-can-i-buy-medigap/when-can-i-buy-medigap.html. Under “I have a pre-existing condition.”