Original Medicare covers a lot — but it doesn’t cover everything, and what it doesn’t cover can leave you exposed to significant out-of-pocket costs. Medicare Supplement insurance, also called Medigap, is the solution. Medigap policies fill the “gaps” in Original Medicare — the deductibles, coinsurance, and other cost-sharing that Medicare doesn’t pay. If you choose Original Medicare over Medicare Advantage, a Medigap policy is almost certainly a critical part of your coverage strategy. This guide explains how Medigap works, what the different plans cover, and how to choose the right one.
What Is Medigap?
Medigap is private health insurance that works alongside Original Medicare (Parts A and B) to cover some or all of Medicare’s cost-sharing requirements. Sold by private insurance companies, Medigap policies are standardized by the federal government — meaning a Plan G sold by one insurance company covers exactly the same benefits as a Plan G sold by another. The only differences between carriers are the premium and the quality of customer service.
Medigap policies do not cover prescription drugs, dental, vision, or hearing — those require separate coverage. Medigap also does not work with Medicare Advantage; you cannot hold a Medigap policy if you’re enrolled in an MA plan.
According to AHIP, approximately 14 million Medicare beneficiaries hold Medigap policies. The average Medigap enrollee is significantly less likely to report financial hardship from medical bills than Original Medicare beneficiaries without Medigap, which speaks to the protection these policies provide.
The Standard Medigap Plans
There are currently 10 standardized Medigap plans available in most states, labeled A through N (not all plans are available in all states; Massachusetts, Minnesota, and Wisconsin have their own standardization systems). Here’s what each covers:
- Plan A: The most basic plan. Covers Part A hospital coinsurance and hospital costs up to an additional 365 days after Medicare benefits are exhausted; Part B coinsurance or copayment; blood (first 3 pints); Part A hospice care coinsurance.
- Plan B: Everything in Plan A plus the Part A hospital deductible.
- Plan D: Everything in Plan A plus Part A deductible, skilled nursing facility (SNF) coinsurance, and foreign travel emergency coverage (80%, up to plan limits).
- Plan G: The most comprehensive plan available to new Medicare beneficiaries. Covers everything except the Part B deductible. Includes Part A deductible, Part B excess charges, SNF coinsurance, and foreign travel emergency.
- Plan N: Similar to Plan G but requires copays of up to $20 for office visits and $50 for emergency room visits. Does not cover Part B excess charges.
- Plan K and Plan L: Cost-sharing plans with lower premiums but requiring 50% (Plan K) or 25% (Plan L) of certain covered costs, with annual out-of-pocket limits.
Note: Plans C and F (which covered the Part B deductible) are no longer available to Medicare beneficiaries who became eligible on or after January 1, 2020. If you became eligible before that date and enrolled in a Plan C or F, you can keep it. If you became eligible after, Plan G is effectively the most comprehensive option available.
Plan G vs. Plan N: The Most Common Choice
For most new Medicare beneficiaries, the practical decision comes down to Plan G or Plan N. Here’s the comparison:
Plan G covers virtually everything Original Medicare doesn’t (except the Part B deductible of $257/year in 2025). With Plan G, you pay your Part B deductible at the start of the year, then essentially nothing for covered Medicare services for the rest of the year. Plan G provides maximum financial predictability — you know exactly what you’ll owe.
Plan N has lower premiums than Plan G but requires copays of up to $20 for physician office visits and $50 for emergency room visits that don’t result in inpatient admission. Plan N also does not cover Part B excess charges — amounts that doctors who don’t accept Medicare assignment can charge above the Medicare-approved amount (up to 15% above). Plan N is a good choice if you see doctors infrequently and want lower premiums.
The break-even analysis: if Plan G costs $50/month more than Plan N, you need to make 2.5 office visits per month at the maximum $20 copay before Plan G becomes cheaper. Most people don’t visit the doctor that frequently, making Plan N the better financial value for healthy beneficiaries who see providers sparingly.
When to Buy Medigap: The Enrollment Window
The most important thing to understand about Medigap is the enrollment window. Your Medigap Open Enrollment Period is a 6-month window that begins the first month you’re both age 65+ and enrolled in Medicare Part B. During this window, you have guaranteed issue rights — insurance companies must sell you any Medigap policy they offer in your state at standard rates, regardless of your health history. They cannot deny coverage or charge higher premiums based on pre-existing conditions.
Outside of your open enrollment period, Medigap insurers can use medical underwriting in most states — meaning they can deny your application, charge you significantly higher premiums, or exclude pre-existing conditions based on your health history. If you have significant health conditions, you may be unable to get Medigap coverage at all if you miss the open enrollment window.
This is the most critical warning for people considering Medicare Advantage: if you enroll in MA at 65 and later want to switch to Original Medicare with Medigap, you may face medical underwriting when you apply for Medigap. If your health has declined during your MA enrollment, you might not be able to get a Medigap policy at any price. A few states (Connecticut, Massachusetts, Maine, New York) have continuous open enrollment for Medigap, but most do not.
Medigap Premiums and Pricing Methods
Medigap premiums vary by plan, carrier, and location. For a 65-year-old woman, Plan G premiums range from approximately $100 to $250+ per month depending on the state and carrier. Men typically pay slightly less than women. Premiums also vary by pricing methodology:
- Community-rated (no-age-rated): Everyone pays the same premium regardless of age. Premiums may increase with inflation but not with your age. Generally the most cost-effective option over time for younger enrollees.
- Issue-age-rated: Premiums are based on your age when you first buy the policy and don’t increase as you age (though they may increase with inflation). Younger buyers get lower rates that don’t age-increase.
- Attained-age-rated: Premiums start lower but increase as you age. Can become quite expensive in your 80s. Most common pricing method.
Frequently Asked Questions
Does Medigap cover prescription drugs?
No. Medigap policies don’t include prescription drug coverage. You’ll need a separate Part D Prescription Drug Plan if you want drug coverage. Only Medigap policies sold before 2006 included prescription drug coverage.
Can I have Medigap if I’m under 65 on Medicare due to disability?
Under federal law, Medigap insurers are not required to sell policies to beneficiaries under 65. Some states require it; others don’t. In states that don’t require it, under-65 beneficiaries may have limited or no access to Medigap. Contact your state insurance department to understand your rights.
Do I have to use specific doctors with Medigap?
No. Medigap works wherever Medicare is accepted. If your doctor accepts Medicare, your Medigap plan follows. There are no networks, no referrals, and no prior authorizations with Medigap — you have complete freedom of provider choice.
What is a Part B excess charge?
If a doctor does not accept Medicare assignment, they can charge up to 15% above the Medicare-approved amount. This excess charge is covered by Plans G, F, and a few others, but not Plan N. Most doctors accept Medicare assignment, but if you see specialists at major academic centers, it’s worth verifying before choosing a plan that doesn’t cover excess charges.
Choosing the right Medigap plan requires understanding your health needs, budget, and risk tolerance. At Garden State Benefits, Paul Z Olah helps Medicare beneficiaries across NJ and 25 other states navigate their Medigap options during the critical enrollment window — and beyond. Call 856-880-6340 or email paul@gardenstatebenefits.com to compare plans with no pressure.