Medigap (Medicare Supplement Insurance) covers the out-of-pocket costs that Original Medicare leaves behind, including coinsurance, copayments, and deductibles. These are standardized plans sold by private insurers, labeled by letter (A, B, C, D, F, G, K, L, M, and N), and each letter offers the same benefits no matter which company sells it. The differences between plans come down to how much of each cost category they pick up.
Core Benefits Every Plan Covers
All ten Medigap plans share a foundation of coverage. Every plan pays 100% of Part A coinsurance and hospital costs, plus an additional 365 days of inpatient hospital care after your regular Medicare benefits run out. That extra year of coverage is significant: once Medicare’s 60 lifetime reserve days are exhausted, you’d otherwise face the full daily hospital cost on your own.
Every plan also covers Part B coinsurance or copayments, which is the 20% share you normally owe for doctor visits, outpatient procedures, lab work, and other services covered under Part B. Plans K and L are the exceptions here. They cover 50% and 75% of that coinsurance respectively, rather than the full amount.
The first three pints of blood used in a medical procedure are another universal benefit. Plans A through G, M, and N cover this cost completely, while Plan K covers 50% and Plan L covers 75%.
Hospital and Hospice Coverage
When you’re admitted to a hospital under Medicare Part A, you face a deductible for each benefit period (currently over $1,600). Most Medigap plans cover this deductible in full. Plans A and K are partial exceptions: Plan K covers 50% and Plan L covers 75%, while Plan M covers 50% of the Part A deductible.
Hospice care coinsurance, which covers respite care and other Part A services during end-of-life care, is included in every Medigap plan. Again, Plans K and L pay their partial percentages (50% and 75%), while the remaining plans cover it fully.
Skilled Nursing Facility Coinsurance
After a qualifying hospital stay, Medicare covers the first 20 days of skilled nursing facility care in full. Days 21 through 100 come with a daily coinsurance that can exceed $200. Plans C, D, F, G, M, and N cover 100% of that coinsurance. Plan K covers 50%, Plan L covers 75%, and Plans A and B don’t cover it at all. If you anticipate needing rehabilitation or extended nursing care after a hospitalization, this benefit is worth paying attention to when choosing a plan.
Foreign Travel Emergency Care
Original Medicare generally doesn’t cover health care outside the United States. Most Medigap plans fill that gap for emergencies. Plans C, D, F, G, M, and N pay 80% of billed charges for medically necessary emergency care abroad after you meet a $250 annual deductible. There’s a $50,000 lifetime cap on this benefit. Plans A, B, K, and L don’t include foreign travel coverage. If you travel internationally, this is one of the more practical reasons to choose a plan that includes it.
How Plans Differ by Letter
The most comprehensive plans are F and G. Plan F covers every gap in Original Medicare, including the Part B deductible. Plan G covers everything except that Part B deductible, which makes it slightly cheaper in monthly premiums while leaving you responsible for one relatively small annual cost. Plan F is no longer available to people who became newly eligible for Medicare on or after January 1, 2020, making Plan G the most popular choice for new enrollees.
Plan C is similar to Plan F and carries the same eligibility restriction for those new to Medicare after 2020. Plans D and M offer solid coverage but skip the Part B deductible and (in M’s case) only cover half the Part A deductible. Plan N covers most costs but requires small copayments for some office and emergency room visits, and it doesn’t cover Part B excess charges (the amount a doctor can bill above Medicare’s approved rate).
Plans K and L take a different approach entirely. They cover a percentage of most benefits (50% for K, 75% for L) rather than the full amount, but they cap your annual out-of-pocket spending. Once you hit that cap, the plan covers 100% of approved costs for the rest of the year. These plans carry lower premiums and work best for people who want catastrophic protection without paying for full first-dollar coverage.
What Medigap Does Not Cover
Medigap fills gaps in Original Medicare, but it doesn’t expand what Medicare covers. If Medicare doesn’t pay for a service, your Medigap plan won’t either. That means no coverage for dental care, vision exams, hearing aids, or long-term custodial care in a nursing home. Private-duty nursing and cosmetic surgery are also excluded.
Prescription drugs are a notable exclusion. Medigap plans sold after 2005 cannot include drug coverage. If you need help paying for medications, you’ll need to enroll in a separate Medicare Part D prescription drug plan. Some people who bought Medigap policies before 2006 may still have drug benefits grandfathered in, but new enrollees won’t find this option.
Each Medigap policy covers only one person. If both you and your spouse want supplemental coverage, you’ll each need your own policy.
How Premiums Are Set
While benefits are standardized, prices are not. Two companies selling Plan G in the same zip code can charge very different premiums. Insurers use one of three pricing methods. Community-rated plans charge the same premium to everyone regardless of age. Issue-age plans base your premium on the age you were when you first bought the policy, so enrolling younger locks in a lower starting rate. Attained-age plans start lower but increase as you get older, reflecting rising health care costs with age. Knowing which method your insurer uses matters because it affects how much you’ll pay five, ten, or twenty years from now.
When You Can Enroll
Your best window to buy a Medigap policy is during the six-month Medigap Open Enrollment Period, which starts the first month you’re both 65 or older and enrolled in Medicare Part B. During this window, insurers must sell you any Medigap plan they offer at the standard price, regardless of your health. They can’t charge more for pre-existing conditions or deny you coverage.
Outside that window, insurers in most states can use medical underwriting, meaning they can review your health history and either charge higher premiums or refuse to sell you a policy. There are specific situations, called guaranteed issue rights, where insurers must sell you a policy without underwriting even after your open enrollment has passed. These typically apply when you lose other coverage through no fault of your own, such as when a Medicare Advantage plan leaves your area or an employer plan ends.