Medigap is extra insurance you buy from a private company to cover the out-of-pocket costs that Original Medicare leaves behind. These include copayments, coinsurance, and deductibles for services under Part A (hospital insurance) and Part B (medical insurance). You must already have Original Medicare to buy a Medigap policy. It doesn’t replace Medicare; it works alongside it, picking up some or all of the costs Medicare approves but doesn’t fully pay.
What Medigap Covers
Every Medigap plan covers a core set of costs. The big one: Part A coinsurance and hospital costs for up to an additional 365 days after your regular Medicare benefits run out. All ten standardized plans cover this at 100%. All plans also cover Part B coinsurance or copayments (the portion you owe after Medicare pays its share for doctor visits, outpatient care, and similar services), the blood benefit for the first three pints, and Part A hospice care coinsurance.
Beyond that core, plans differ. More comprehensive plans also cover skilled nursing facility coinsurance, the Part A deductible, the Part B deductible, excess charges from doctors who bill above the Medicare-approved amount, and emergency medical care during foreign travel. The most basic plan, Plan A, covers none of these extras. Plans like G and the now-restricted Plan F cover nearly all of them.
Medigap does not cover prescription drugs. Since the creation of Medicare Part D in 2003, new Medigap policies have been barred from including drug coverage. If you want help paying for medications, you need a separate Part D plan. Medigap also won’t cover anything Original Medicare itself doesn’t cover: dental care, vision exams for glasses, hearing aids, long-term care, cosmetic surgery, or massage therapy.
The 10 Standardized Plans
Federal law standardizes Medigap into ten plans, labeled A, B, C, D, F, G, K, L, M, and N. Each letter offers the same benefits no matter which insurance company sells it. A Plan G from one insurer covers the exact same things as a Plan G from another. The only difference between companies is the price and quality of customer service.
Here’s how the most common plans break down:
- Plan A: The most basic. Covers the core benefits only, with no coverage for deductibles, skilled nursing, excess charges, or foreign travel.
- Plan G: The most popular plan available to new enrollees. Covers everything except the Part B deductible ($283 in 2026). Also available as a high-deductible version, where you pay $2,870 out of pocket (as of 2025) before the plan kicks in.
- Plan N: Similar to Plan G but with small copayments for some office visits and emergency room visits. Doesn’t cover Part B excess charges.
- Plan K and Plan L: Cost-sharing plans that cover benefits at 50% and 75% respectively, with annual out-of-pocket limits ($8,000 for Plan K and $4,000 for Plan L in 2026). Once you hit that cap, the plan pays 100% for the rest of the year.
- Plan F: The most comprehensive option, covering everything including the Part B deductible. However, it’s no longer available to anyone who turned 65 on or after January 1, 2020. If you were eligible for Medicare before that date, you can still buy it.
- Plan C: Similar to Plan F, and subject to the same restriction for people newly eligible after January 1, 2020.
Plans D and M fall in the middle. Plan D covers most benefits but skips the Part B deductible and excess charges. Plan M covers the Part A deductible at only 50% instead of 100%.
How Premiums Are Set
Two people buying the same lettered plan from different companies can pay very different monthly premiums. That’s because insurers use one of three pricing methods, and the one your insurer uses matters a lot over time.
Community-rated plans charge everyone the same premium regardless of age. A 65-year-old and a 78-year-old pay the same base price. These tend to cost more when you first enroll but don’t climb as you get older.
Issue-age-rated plans base your premium on the age you were when you first bought the policy. Your rate won’t increase just because you had a birthday, though it can still rise due to inflation or other factors.
Attained-age-rated plans start with the lowest premiums but increase as you age, reflecting rising healthcare costs over time. These are the most common type, and they can become significantly more expensive in your 70s and 80s.
When comparing plans, it’s worth asking each insurer which rating method they use. A policy that looks cheapest at 65 may end up costing the most by 75.
When to Enroll
Timing is everything with Medigap. You get one six-month Medigap Open Enrollment Period, and it starts the first month you have Part B and are 65 or older. During this window, no insurance company can refuse to sell you any Medigap plan it offers, charge you more because of health problems, or make you wait for coverage to begin (except for pre-existing conditions in some cases).
This is a one-time window. It does not repeat every year like Medicare’s annual Open Enrollment Period. If you try to buy a Medigap plan after those six months have passed, insurers can use medical underwriting, meaning they can review your health history, charge higher premiums, or deny you coverage altogether.
There are exceptions. Certain situations trigger what’s called “guaranteed issue rights,” where an insurer must sell you a policy regardless of your health. Losing coverage from an employer plan or a Medicare Advantage plan, for example, can qualify. Individual states may also offer additional protections beyond federal rules, so checking with your state insurance department is worth the effort if you’ve missed the initial window.
Medigap vs. Medicare Advantage
Medigap and Medicare Advantage (Part C) are two fundamentally different ways to handle the costs that Original Medicare doesn’t cover, and you can’t have both at the same time.
With Medigap, you keep Original Medicare. You can see any doctor or specialist in the country who accepts Medicare, with no referrals needed. Your Medigap plan simply pays whatever portion of the bill it’s designed to cover. The trade-off is that you pay a monthly premium on top of your Part B premium, and you need a separate Part D plan for prescriptions.
Medicare Advantage replaces Original Medicare entirely. These plans are run by private insurers and often include prescription drug coverage, dental, vision, and hearing benefits bundled in. They typically cost less per month (some have $0 premiums), but they use provider networks. You may need referrals to see specialists, and going out of network can mean higher costs or no coverage at all.
The choice often comes down to how much flexibility you want in choosing providers versus how much you’re willing to pay in monthly premiums. People who travel frequently, see specialists in different states, or want predictable costs with few surprises tend to prefer Medigap. People who want lower premiums and are comfortable staying within a network often lean toward Medicare Advantage.