Medigap (Medicare Supplement Insurance) covers the out-of-pocket costs that Original Medicare leaves behind, including deductibles, coinsurance, copayments, and a few benefits Medicare doesn’t offer at all. The most significant of these is emergency medical care during foreign travel, which Original Medicare almost never pays for. But the bulk of Medigap’s value comes from filling the specific dollar gaps in Parts A and B.
The Hospital Costs Medigap Picks Up
Original Medicare covers inpatient hospital stays, but it charges you a deductible of $1,676 in 2025 (rising to $1,736 in 2026) each time a new benefit period begins. That’s not an annual deductible. If you’re hospitalized, discharged, and readmitted after 60 days, you pay it again. Most Medigap plans cover this deductible entirely.
Hospital stays also come with coinsurance after day 60. From days 61 through 90, Medicare charges you a daily coinsurance. Beyond day 90, you start dipping into your lifetime reserve days, which carry an even higher daily cost. Medigap plans cover the coinsurance for both of these periods. Some plans also add up to 365 extra hospital days after your Medicare benefits run out, a safety net Original Medicare simply doesn’t provide.
Skilled Nursing Facility Coinsurance
If you need care in a skilled nursing facility after a qualifying hospital stay, Medicare covers the first 20 days fully. Starting on day 21, you owe a coinsurance of $204.50 per day in 2025, and this continues through day 100. For a full 80-day stretch of coinsurance, that adds up to over $16,000. Most Medigap plans cover this coinsurance at 100%, though Plans K and L cover it at 50% and 75%, respectively.
Part B Coinsurance and Copayments
This is where Medigap saves money on everyday medical care. Original Medicare Part B covers doctor visits, outpatient procedures, lab work, and other services, but you’re responsible for 20% of the Medicare-approved amount after meeting your annual deductible. There’s no cap on that 20%. A $50,000 outpatient surgery leaves you owing $10,000. A cancer treatment costing $200,000 means $40,000 out of your pocket.
Every Medigap plan covers at least a portion of Part B coinsurance. Plans A, B, C, D, F, G, M, and N cover it at 100% (with some caveats for Plan N). Plans K and L cover 50% and 75%, respectively. This is the single most valuable benefit for people who face high-cost outpatient care.
Plan N handles Part B coinsurance slightly differently. It covers 100% of your Part B costs except for small copayments: up to $20 for some office visits and up to $50 for emergency room visits where you aren’t admitted to the hospital. In exchange, Plan N typically has lower monthly premiums than Plan G.
Part B Excess Charges
Most people don’t realize this gap exists. When a doctor accepts Medicare but doesn’t “accept assignment,” they can charge up to 15% more than the Medicare-approved amount. You pay that difference out of pocket, and Original Medicare doesn’t cover it. Only Medigap Plans F and G cover 100% of these excess charges. Plan N and most other plans don’t cover them at all.
In practice, the majority of doctors accept assignment, so excess charges aren’t common. But if your specialists don’t, Plan G’s excess charge coverage can save you from unexpected bills.
Blood Transfusion Costs
Under Original Medicare, you’re responsible for the first three pints of blood you receive during a covered procedure. This applies under both Part A and Part B. Most Medigap plans cover this cost fully. Plans K and L cover it at 50% and 75%. It’s a small benefit, but one that catches people off guard when they need surgery or a transfusion and see a bill they didn’t expect.
Foreign Travel Emergency Care
This is the one area where Medigap covers something Original Medicare genuinely does not pay for, rather than simply filling a cost-sharing gap. Original Medicare provides almost no coverage outside the United States.
Most Medigap plans (C, D, F, G, M, and N) include foreign travel emergency coverage. The benefit kicks in for emergencies that begin within the first 60 days of your trip. After you meet a $250 annual deductible, the plan pays 80% of medically necessary emergency care you receive abroad. There’s a lifetime cap of $50,000. That won’t cover a prolonged hospitalization overseas, but it handles most emergency situations like a broken bone, heart event, or acute illness while traveling.
Plans A, B, K, and L do not include foreign travel emergency benefits.
What Medigap Does Not Cover
Medigap fills cost-sharing gaps in Original Medicare, but it doesn’t expand what Medicare covers. If Medicare doesn’t cover a service, Medigap won’t either. That means no coverage for:
- Prescription drugs. You need a separate Part D plan for that.
- Dental, vision, and hearing care. Routine cleanings, eyeglasses, and hearing aids fall outside Original Medicare and Medigap alike.
- Long-term custodial care. Extended nursing home stays or in-home assistance with daily activities aren’t covered by Medicare or Medigap.
Medigap also cannot be combined with a Medicare Advantage plan. If you’re enrolled in Medicare Advantage (Part C), a Medigap policy won’t pay your cost-sharing. Medigap works only with Original Medicare (Parts A and B).
How Plan Choice Affects Your Coverage
There are ten standardized Medigap plans, labeled A through N (with some letters skipped). Every insurer selling Plan G, for example, offers the exact same benefits. The only differences between insurers are price and customer service.
Plan G is the most comprehensive plan available to people who became eligible for Medicare after January 1, 2020. It covers everything except the annual Part B deductible ($257 in 2025). Plan F covers even the Part B deductible, but it’s only available to people who were eligible for Medicare before 2020.
Plan N is the most popular alternative to Plan G. It skips Part B excess charge coverage and adds small copayments for certain visits, but its premiums are noticeably lower. For people whose doctors all accept assignment, Plan N often provides nearly identical protection at a lower cost.
Plans K and L are the budget options, covering major benefits at 50% or 75% instead of 100%. They do include an annual out-of-pocket limit ($7,060 and $3,530 in 2025, respectively), which none of the other plans need because they cover costs so thoroughly.
Timing Your Enrollment Matters
Your Medigap Open Enrollment Period lasts six months, starting the first month you have Part B and are 65 or older. During this window, insurers cannot deny you coverage, charge you more for health conditions, or reject your application for any reason. Once that window closes, insurers in most states can use medical underwriting, meaning a pre-existing condition could make coverage more expensive or unavailable. Enrolling during that initial six-month period locks in your right to buy any Medigap plan at standard rates regardless of your health.