Medigap (Medicare Supplement) Guide 2026: Plan G vs Plan N, Enrollment Timing, and Costs

Medigap fills the ‘gaps’ Medicare leaves behind — why do you need it?

Original Medicare (Part A hospital insurance plus Part B medical insurance) does not pay 100% of your care. Part A leaves an inpatient deductible, Part B leaves an annual deductible plus a 20% coinsurance on approved services, and — critically — Original Medicare has no annual out-of-pocket maximum. That means a serious illness could pile up 20% of very large bills with no ceiling. Medigap (formally Medicare Supplement insurance) is private coverage designed to fill exactly those gaps.

The key idea is that Medigap supplements rather than replaces Medicare. Medicare processes the claim first, then Medigap pays the remaining cost-sharing according to your plan. That converts the uncertainty of “how much will this visit cost?” into a predictable monthly premium — which is why Medigap appeals to people who value budgeting certainty over the lowest possible premium.

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This article does not recommend any specific insurance product. It is general educational information. Confirm any real enrollment decision with a licensed insurance professional or free official Medicare counseling such as your State Health Insurance Assistance Program (SHIP).

What cost-sharing does Original Medicare leave behind?

To understand Medigap, you first need to know the costs Medicare leaves on the table. Exact dollar figures change every year, so the focus here is on the structure, not specific amounts.

• Part A deductible: charged per benefit period for inpatient hospital stays; you could owe it more than once in a year.
• Part A coinsurance: daily charges kick in after a set number of inpatient days.
• Part B deductible: an outpatient deductible that resets annually.
• Part B coinsurance: even after the deductible, you owe roughly 20% of approved charges.
• Part B excess charges: extra amounts some providers can bill above the Medicare-approved rate.

Medigap plans are labeled by letter based on how many of these items they cover. As a rule, broader coverage means a higher premium.

How do the standardized Medigap plans differ? (comparison table)

Medigap’s defining feature is standardization. Plans run from A through N, and any plan with the same letter offers legally identical benefits (three states — Wisconsin, Massachusetts, and Minnesota — use their own systems). So the only things a shopper is really comparing are premium, insurer stability, and service.

Feature	Plan G	Plan N	Plan K	Plan F (closed to new)
Part A deductible	Full	Full	50%	Full
Part B deductible	You pay	You pay	You pay	Covered
Part B coinsurance (20%)	Full	Mostly full (small copays)	50%	Full
Part B excess charges	Covered	You pay	You pay	Covered
Office / ER copays	None	Small	N/A	None
Relative premium	Mid–high	Mid	Low	High

The most popular choice is Plan G: once you pay the Part B deductible yourself, nearly all remaining cost-sharing is covered. Plan N fits people willing to accept small copays and excess-charge risk in exchange for a lower premium. Plan K and Plan L are cost-sharing designs — lower premiums, but you pay a larger share up to an annual out-of-pocket limit.

Medigap vs Medicare Advantage — what’s the difference? (comparison table)

The single most confusing point for seniors is the difference between Medigap and Medicare Advantage (Part C). They are mutually exclusive — you cannot enroll in both.

Factor	Medigap (Supplement)	Medicare Advantage (Part C)
Basic structure	Original Medicare + supplement	Private plan replaces Medicare
Doctor/hospital choice	Anyone who accepts Medicare	Network limits (HMO/PPO)
Monthly premium	Relatively higher	Lower (even $0 plans exist)
Cost predictability	High, stable	Copays at each visit
Extras (dental/vision/drugs)	None (Part D separate)	Often bundled in
Prior authorization	Rare	Often required
Travel / nationwide use	Strong	Region/network limited

Medigap tends to favor people who prize freedom of provider choice and predictable costs — those who travel, split time between states, or see specialists often. Medicare Advantage can be attractive for people who want low premiums and bundled extras and are comfortable within a local network. The honest answer isn’t “one is better”; it’s that the right choice depends on your lifestyle and health.

Timing is everything — the 6-month Medigap Open Enrollment window

The most important concept in Medigap is the Medigap Open Enrollment Period. It begins the first month you are both 65 or older and enrolled in Medicare Part B, and it lasts exactly six months.

During those six months you have a guaranteed issue right: an insurer cannot deny you or raise your premium because of your health, even with pre-existing conditions. This window is essentially once in a lifetime, and missing it is hard to undo.

What is medical underwriting, and why is waiting risky?

Once your 6-month window closes, most states allow insurers to apply medical underwriting to Medigap applications. At that point a company can:

• Deny your application based on pre-existing conditions,
• Charge you a higher premium based on health, or
• Impose a waiting period for certain conditions.

This is why starting with Medicare Advantage and hoping to switch to Medigap later can backfire — you may not be able to get the plan you want at all. Some states (such as New York and Connecticut) offer continuous or annual guaranteed-issue rights, so always check your state’s rules. The belief that “I’ll start cheap on Advantage and move to Medigap later” is the most common and most dangerous misconception.

How are premiums set? — the three pricing methods

Why does the same Plan G cost different amounts across companies and ZIP codes? The benefits are identical, but the rating method is not — and it makes a big difference to what you pay over a lifetime.

Pricing method	How it works	Long-term behavior
Issue-age	Premium set by your age at purchase	Won’t rise because you got older
Attained-age	Premium rises with your current age	Cheap early, can climb sharply later
Community-rated	Everyone in an area pays the same	Age-neutral, tends to be stable

On top of the rating method, inflation, local medical costs, tobacco use, gender discounts, and the insurer’s loss experience all influence rate increases. Attained-age policies in particular can look cheap at 65 but become burdensome in your 80s — so picking “whatever is cheapest right now” is a mistake.

Who is Medigap right for — and who should be cautious?

A good fit if: you want freedom to choose any doctor or hospital, you travel or live in multiple states and need nationwide coverage, you’d rather pay a fixed premium than face a surprise large bill, or you have chronic conditions requiring frequent specialist care.

Be cautious if: a higher monthly premium strains your budget (Advantage may cost less), you’ve already missed your Open Enrollment window and would face underwriting, or you want dental, vision, and drug benefits bundled in one plan. Also remember Medigap is a single-person policy — even married couples must each enroll separately.

Practical checkpoints for U.S.-based and immigrant families

Three things families — including those sponsoring or immigrating older parents — should keep in mind when weighing Medigap in the U.S.

1. Confirm eligibility first. Medicare generally requires being 65+ and having paid enough into the system (typically 10 years / 40 credits) or qualifying through a spouse’s record. Without that, you may need to buy premium Part A, or look at Medicaid or Marketplace alternatives instead.
2. Use neutral counseling and language support. Every state’s SHIP offers free, unbiased counseling, and some areas provide multilingual help. Brokers may be biased toward specific carriers, so cross-check with official sources.
3. Compare total annual cost, not just the premium. Weigh (Medigap premium + Part B premium + Part D drug plan) against (Advantage premium + copays at each visit) as a yearly total — and factor in the value of predictability if your health declines later.

One more note: for U.S. tax purposes, medical expenses above a percentage of adjusted gross income may be deductible if you itemize. Because this depends on your situation, confirm with a tax professional.

Common mistakes and caveats

• Forgetting Part D drug coverage. Medigap does not cover prescriptions. Enroll in Part D on time or face a lifelong late-enrollment penalty.
• Letting Open Enrollment slip by. Losing your one no-underwriting window is the biggest avoidable loss.
• Chasing price and ignoring the carrier. Same plan means same benefits, but rate-increase history and financial strength vary by company.
• Assuming a couple can share one policy. Medigap is individual.
• Underestimating the difficulty of switching from Advantage to Medigap. Underwriting can block the return trip.

Related reading

• Capital gains tax guide 2026
• SCHD dividend ETF guide
• Qualified Opportunity Zone fund tax strategy
• Charitable remainder trust tax strategy

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This article is general educational information about Medicare and Medigap and is not insurance, legal, or tax advice. Specific plan benefits, premiums, and eligibility vary by year and by state, so before making any enrollment decision, confirm the details with official Medicare resources (Medicare.gov), your state’s SHIP counselors, or a licensed insurance professional.