Medicare Supplement Plans Explained: Medigap Coverage, Costs, and How to Choose

Medicare Supplement plans — officially called Medigap — are private insurance policies that cover the out-of-pocket costs that Original Medicare leaves behind. When your parent goes to the doctor or has a hospital stay under Original Medicare, Medicare pays its share (typically 80% for Part B services) and your parent pays the rest. A Medigap plan picks up some or all of that remaining bill.

The reason these plans exist is straightforward: Original Medicare has no annual out-of-pocket maximum. If your parent has a major medical event — cancer treatment, a serious surgery, an extended hospital stay — the 20% coinsurance on Part B alone can add up to tens of thousands of dollars with no cap. A Medigap plan puts a ceiling on that exposure.

This article explains how Medigap plans work, what each lettered plan covers, what they cost in 2026, and how to make a choice that actually fits your parent's situation.

How Medigap plans work

The basics

Medigap plans are sold by private insurance companies, but the benefits are standardized by the federal government. A Plan G from one company covers exactly the same things as a Plan G from another company. The only differences between companies selling the same letter plan are the premium price and the quality of customer service.

Your parent must have Original Medicare (Parts A and B) to buy a Medigap plan. The Medigap plan works alongside Original Medicare — it doesn't replace it. When your parent receives a covered medical service, Medicare pays its share first, then the Medigap plan pays its share of the remaining costs.

Medigap plans do not cover prescription drugs. Your parent needs a separate Medicare Part D plan for drug coverage.

What Medigap cannot do

• Cannot be combined with Medicare Advantage. Your parent has either Original Medicare + Medigap, or a Medicare Advantage plan. Not both.
• Covers only one person. If both parents need coverage, each needs their own policy.
• Does not cover dental, vision, hearing, or long-term care. These gaps exist in Original Medicare and Medigap does not fill them.

The lettered plans: what each one covers

There are 10 standardized Medigap plans, labeled A through N (with some letters skipped). In practice, only a few plans are commonly sold. Here's what they cover:

Core benefits (all plans include these)

Every Medigap plan covers at minimum:

• Part A hospital coinsurance and 365 additional days of hospital coverage after Medicare benefits run out
• Part B coinsurance (the 20% your parent would otherwise pay) or copayments
• The first 3 pints of blood each year

Plan-by-plan comparison (most popular plans)

*Plan F is only available to people who became eligible for Medicare before January 1, 2020.

The plans most people actually buy

Plan G is the most popular Medigap plan sold today, and for good reason. It covers everything except the Part B deductible ($257/year). After your parent pays that $257 once per year, Plan G covers all remaining Medicare cost-sharing — hospital deductibles, coinsurance, skilled nursing costs, excess charges, everything. For families who want predictable costs and peace of mind, Plan G is the standard recommendation.

Plan N is the budget-friendly alternative to Plan G. It covers most of the same benefits but with two differences: it doesn't cover Part B excess charges, and it charges small copays for some office visits (up to $20 for doctor visits, up to $50 for emergency room visits that don't result in admission). In exchange, Plan N premiums are typically $30-$50 less per month than Plan G.

Plan F was the most comprehensive plan, covering even the Part B deductible. But it's been closed to new enrollees since 2020, which means the risk pool is aging. Premiums for Plan F are rising faster than other plans because no healthy new members are joining. If your parent already has Plan F, they can keep it, but they should monitor the premiums annually.

High Deductible Plan G is a less well-known option for healthy seniors. It has the same benefits as Plan G, but your parent pays a high deductible ($2,870 in 2026) before the plan starts covering costs. In exchange, the monthly premium is dramatically lower — often $40-$60/month compared to $150-$250 for standard Plan G. If your parent is healthy and rarely uses medical services, the math can work strongly in their favor.

What Medigap plans cost in 2026

Medigap premiums vary significantly based on:

• Location — premiums in Florida or New York are typically much higher than in the Midwest
• Age — older applicants pay more (with some pricing methods)
• Gender — women often pay slightly less
• Tobacco use — smokers pay higher premiums
• The insurance company — since all Plan G's cover the same benefits, the only difference is the price and service

Typical monthly premium ranges (2026)

These are broad national ranges. Your parent's actual premium depends on their specific zip code, age, and the company they choose. Premiums also increase every year — typically 3-8% annually, though some companies have larger or smaller increases.

Pricing methods matter

Insurance companies use one of three pricing methods, and this affects how premiums change over time:

• Community-rated (no-age-rated): Everyone pays the same premium regardless of age. The initial premium may be higher for younger enrollees, but it rises more slowly over time.
• Issue-age-rated: The premium is based on the age when your parent first buys the policy. It doesn't increase due to aging (though it can still increase for inflation and other factors).
• Attained-age-rated: The premium is based on your parent's current age and increases as they get older. This is the most common method. The premium starts low but rises more steeply over time.

For a parent enrolling at 65, an attained-age plan may look cheapest initially. But by age 80, the premium may have doubled or tripled. An issue-age or community-rated plan may cost more upfront but is more predictable over the long term. This is a detail most people don't think about at enrollment, and it can cost thousands over a decade.

When to enroll: the Medigap Open Enrollment Period

The most important thing to understand about Medigap is the Medigap Open Enrollment Period — the 6-month window that starts the month your parent turns 65 and is enrolled in Medicare Part B.

During this window, your parent has a guaranteed issue right to buy any Medigap plan sold in their state, regardless of health conditions. The insurance company cannot deny coverage, charge more, or impose waiting periods for pre-existing conditions.

After this 6-month window closes, your parent can still apply for Medigap, but the insurance company can:

• Deny the application based on health status
• Charge higher premiums for pre-existing conditions
• Impose waiting periods before covering pre-existing conditions

This is why the timing of Medigap enrollment is critical. If your parent is relatively healthy at 65, this is the time to lock in a Medigap plan. If they wait — even a few years — and then develop a health condition, they may not be able to get Medigap at all (or may face significantly higher premiums).

There are limited exceptions where guaranteed issue rights apply outside the open enrollment window (for example, if your parent loses employer coverage or leaves a Medicare Advantage plan within the first 12 months). But these are specific situations, not a general safety net.

AARP-branded Medigap plans

You'll see "AARP Medicare Supplement" plans mentioned frequently. These are Medigap plans underwritten by UnitedHealthcare and sold under the AARP brand. They're standard lettered plans (Plan G, Plan N, etc.) — the coverage is identical to the same lettered plan from any other company. The AARP name doesn't change the benefits.

AARP/UnitedHealthcare is one of the largest Medigap sellers in the country. Their premiums are competitive in some areas and less competitive in others. There's no inherent advantage to choosing an AARP-branded plan over another company's identical lettered plan — compare premiums, check the company's financial strength rating, and read reviews on claims handling.

How to choose the right Medigap plan

Step 1: Decide between Plan G and Plan N

For most families, the real choice comes down to Plan G versus Plan N. Plan G offers complete coverage after the $257 deductible. Plan N is cheaper but has small copays and doesn't cover excess charges.

The deciding factors:

• If your parent sees doctors frequently (12+ visits per year) or has chronic conditions requiring regular specialist visits, Plan G's comprehensive coverage avoids nickel-and-dime copays.
• If your parent is healthy and sees doctors infrequently, Plan N's lower premium saves money month over month, and the occasional $20 copay is minimal.
• Part B excess charges are the wildcard. These occur when a doctor charges more than the Medicare-approved amount. Fewer than 5% of doctors charge excess fees, and many states prohibit them entirely. If your parent's doctors all accept Medicare assignment, excess charges aren't a factor.

Step 2: Compare premiums from multiple companies

Since Plan G from Company A covers the exact same benefits as Plan G from Company B, the comparison is purely about price and company reputation. Get quotes from at least 3-5 insurance companies. Your state's SHIP program (State Health Insurance Assistance Program) can help with this comparison at no cost.

Step 3: Check the pricing method

Ask each company whether their plan is community-rated, issue-age-rated, or attained-age-rated. This determines how fast premiums will grow over the next 10-20 years.

Step 4: Verify the company's financial stability

Look up the insurer's A.M. Best rating. A rating of A- or better indicates strong financial health. This matters because your parent may have this policy for 20+ years — you want the company to still be around and paying claims.

The bottom line for families

Medigap plans solve the biggest financial vulnerability in Original Medicare: the lack of an out-of-pocket maximum. They give your parent predictable healthcare costs and the freedom to see any doctor in the country who accepts Medicare — no networks, no referrals, no prior authorizations.

The trade-off is the monthly premium, plus the need for a separate Part D drug plan. For families who value predictability and provider access, Medigap is typically the stronger choice. For families who are healthy and cost-conscious, Medicare Advantage may offer lower premiums and added benefits (dental, vision) but with network restrictions.

Our Medicare Enrollment Guide includes a Medigap comparison worksheet, a premium tracking tool, and a step-by-step walkthrough of the enrollment process — built for adult children helping their parents make this decision with confidence.