The Basic Mechanics: Two Policies, One Seamless System

Original Medicare pays first. Your Medigap policy pays second. That’s the whole system in one sentence, and once you understand it, everything else clicks into place.

Here’s how it actually works when you go to the doctor or hospital. You receive care from any provider that accepts Medicare. Medicare processes the claim and pays its share — generally 80% of approved costs for Part B services after your deductible, or the bulk of hospital costs under Part A. Then your Medigap insurer automatically gets notified through a process called crossover claims. They pay their portion. You receive an Explanation of Benefits from both. In most cases, you pay nothing out of pocket at the point of service.

That last part is why people love Medigap. You don’t submit claims. You don’t fight with insurers on the phone. You show your red, white, and blue Medicare card, and the billing happens behind the scenes. I’ve heard from dozens of people who were shocked that it was this simple after years of dealing with employer-sponsored insurance headaches.

There are ten standardized Medigap plans available in most states, labeled by letters: A, B, D, G, K, L, M, and N, plus high-deductible versions of F and G. Each plan fills in specific gaps that Original Medicare leaves behind. Those gaps are real money: the 2026 Part A hospital deductible is $1,676 per benefit period, and the 20% coinsurance under Part B has no annual cap. Without a Medigap plan, a serious illness could cost you tens of thousands of dollars even with Medicare.

What Medicare Actually Covers (And Where the Gaps Are)

Medicare Part A covers inpatient hospital care, skilled nursing facility care, some home health, and hospice. Part B covers outpatient care: doctor visits, lab work, durable medical equipment, preventive services, and outpatient procedures. Together, they cover a lot. But they leave gaps that can genuinely ruin someone’s finances.

The Part A deductible is per benefit period, not per year. That distinction matters more than most people realize. If you’re hospitalized, discharged, and then rehospitalized more than 60 days later, you owe that $1,676 deductible again. For someone with a chronic condition requiring multiple hospitalizations in a year, that adds up fast. After 60 days in the hospital, you also owe $419 per day in coinsurance (2026 figures) for days 61 through 90. Most people don’t know those numbers until they’re staring at a bill.

Part B has its own deductible — $257 in 2026 — and then you owe 20% of all approved charges with no out-of-pocket maximum. That 20% is the big one. A $100,000 chemotherapy course leaves you owing $20,000. An MRI, a specialist visit, an outpatient surgery — that 20% accumulates every time. Original Medicare was never designed to be someone’s only coverage, and the Medigap system exists precisely because Congress recognized that when it created the program.

Medigap does not cover everything. It won’t pay for dental, vision, hearing, or prescription drugs. For drug coverage, you need a standalone Part D plan. This is a separate system entirely, and a common source of confusion I’ll address below.

Plan G Is the One Most People Should Buy in 2026

I’ll say it plainly: for most people who are newly eligible for Medicare and want predictable healthcare costs, Plan G is the right choice. Plan G covers the Part A deductible, Part A coinsurance and hospital costs up to 365 additional days after Medicare benefits end, Part B coinsurance (that 20%), skilled nursing facility coinsurance, and foreign travel emergency care up to plan limits.

The only gap Plan G leaves is the 2026 Part B deductible of $257. You pay that once per year, and after that, Plan G covers virtually everything Medicare doesn’t. For a 65-year-old in good health, Plan G premiums typically run between $100 and $180 per month depending on your state and insurer. Someone in Ohio might pay around $120 per month. Someone in Florida or New York could pay considerably more due to state regulations and insurer pricing.

Here’s a comparison of the most popular Medigap plans so you can see what you’re actually getting:

Benefit	Plan G	Plan N	Plan K
Part A deductible	100%	100%	50%
Part B deductible ($257 in 2026)	Not covered	Not covered	Not covered
Part B coinsurance (20%)	100%	100% (with copays)	50%
Skilled nursing coinsurance	100%	100%	50%
Foreign travel emergency	80%	80%	Not covered
Part B excess charges	100%	Not covered	Not covered

Plan N is worth considering if you’re younger, healthy, and don’t see specialists often. It has lower premiums but charges copays of up to $20 for office visits and up to $50 for emergency room visits. It also doesn’t cover Part B excess charges, which apply when doctors don’t accept Medicare assignment. If you see a lot of specialists or use out-of-network providers, Plan N’s savings can evaporate quickly.

The Biggest Mistake I See People Make

The most common and costly mistake I’ve seen over the years is waiting too long to enroll in Medigap — or skipping it altogether for Medicare Advantage thinking you can switch back to Medigap later without any trouble.

Here’s what most people don’t know: Medigap has a guaranteed issue period. When you first turn 65 and enroll in Medicare Part B, you have a six-month window during which no insurer can deny you coverage or charge you more because of your health history. That window opens once and doesn’t reopen. After it closes, insurers in most states can use medical underwriting. They can reject you outright for conditions like diabetes, heart disease, or a history of cancer. They can charge you more based on your health status. That 67-year-old in Ohio who had a heart attack at 66 while enrolled in Medicare Advantage may find that every Medigap insurer she approaches declines her application.

A few states — Connecticut, Massachusetts, New York, and Maine — have year-round guaranteed issue rules that protect you regardless of when you apply. But if you don’t live in one of those states, missing that initial enrollment window is a mistake you may not be able to fix. I’ve talked to people in their 70s who are stuck in Medicare Advantage plans they don’t love because they can’t pass underwriting to get into Medigap. It’s one of the most avoidable situations in all of Medicare planning.

The second mistake is confusing Medigap with Medicare Advantage. They are not the same thing and they cannot be combined. Medicare Advantage replaces Original Medicare. Medigap supplements it. If you’re in a Medicare Advantage plan, your Medigap policy is useless — and illegal for an insurer to sell you knowingly.

Does Medigap Work With Any Doctor?

This is one of the biggest advantages of the Original Medicare plus Medigap combination, and it’s something I think people underestimate. Because your Medigap plan works on top of Original Medicare, your network is essentially every doctor and hospital in the country that accepts Medicare. That’s over 93% of primary care physicians and the vast majority of specialists and hospitals.

You don’t need referrals. You don’t need to check whether a specialist is in-network before your appointment. If you live in rural Ohio and want to be seen at the Cleveland Clinic or go to Mayo Clinic in Minnesota, you can do it without prior authorization. That freedom has real value — not just in convenience, but in health outcomes for people with complex conditions who need access to major academic medical centers.

Medicare Advantage plans, by contrast, often have narrow networks. A plan that looks cheap in January can leave you scrambling if your cardiologist or cancer center drops out of the network mid-year. With Medigap and Original Medicare, that problem doesn’t exist.

Bottom Line

If you’re new to Medicare and want protection from catastrophic out-of-pocket costs without worrying about networks or surprise bills, get Plan G. Enroll during your guaranteed issue window when you first sign up for Part B — don’t wait. The $257 annual deductible you’ll pay out of pocket is a small price for the coverage and peace of mind you get in return.

Frequently Asked Questions

Can I use my Medigap plan at any hospital in the country?

Yes. Because Medigap works with Original Medicare, and Original Medicare is accepted at the overwhelming majority of hospitals and providers nationwide, you’re not restricted to a local network. If a provider accepts Medicare, your Medigap plan works there.

Do I still need Part D if I have a Medigap plan?

Yes. Medigap plans don’t cover prescription drugs. You need a separate standalone Part D plan for drug coverage. Enrolling in Part D when you first become eligible is smart because late enrollment penalties apply if you go without creditable drug coverage for 63 or more consecutive days after your Initial Enrollment Period ends.

What happens if I miss my Medigap open enrollment window?

In most states, you’ll face medical underwriting if you try to buy Medigap outside your guaranteed issue window. Insurers can deny you or charge higher premiums based on your health history. Connecticut, Massachusetts, Maine, and New York have consumer protections that allow year-round enrollment regardless of health status. Everyone else needs to be very intentional about enrolling on time.

Is Medigap worth it if I’m healthy and rarely see doctors?

I’d still say yes for most people, and here’s my reasoning: Medigap isn’t primarily for your routine doctor visits. It’s protection against the year you get a serious diagnosis. Cancer, a stroke, a major surgery — these aren’t things you see coming, and the costs under Original Medicare alone can be devastating. The premium you pay each month is buying you certainty, not just coverage for today.