Medigap Plans Compared: How to Choose the Right Medicare Supplement Plan

Have you ever opened a hospital bill, looked at the amount Medicare paid, and thought, "Wait — I still owe how much?" If so, you have already met the reason Medigap exists. Original Medicare (Part A and Part B) covers a lot, but it was never designed to cover everything. There are deductibles, and for most outpatient care you pay 20% of the bill — with no yearly limit on that 20%. Medigap, also called Medicare Supplement Insurance, is a private policy that helps pay some of those leftover costs. This guide walks through how the plans compare, why one letter became the most popular, and when to buy so you cannot be turned down.

1. What Medigap Does (and Does Not Do)

Medigap works alongside Original Medicare. Medicare pays its share first, and then your Medigap policy pays some or all of what is left, depending on the plan you choose. Because the benefits of each lettered plan are standardized by law, a Plan G from one insurance company covers exactly the same things as a Plan G from another. Only the price and the company behind it differ.

Just as important is what Medigap does not cover. It does not include prescription drugs, so most people pair it with a separate Part D drug plan. It does not pay for routine dental, vision, or hearing care, and it does not cover long-term care. Think of it as protection for your Medicare-covered medical bills — hospital stays, doctor visits, tests, and treatments — not an everything policy.

2. The 10 Standard Plans, From A to N

In most states, Medigap policies are sold under the letters A, B, C, D, F, G, K, L, M, and N. (Massachusetts, Minnesota, and Wisconsin use a different system.) Each letter is a different package of benefits. In plain terms:

• Plans A and B are the most basic. They cover the Part A and Part B coinsurance and hospital costs, but leave more gaps than the others.
• Plans C and F were once the most complete, but they are only available if you were eligible for Medicare before January 1, 2020.
• Plan G covers nearly everything except the annual Part B deductible.
• Plan N is similar to G but with small copays for some doctor and emergency visits, and it does not cover "excess charges" (explained below).
• Plans K and L pay a percentage (50% or 75%) of most costs, but they include a yearly out-of-pocket limit, after which they pay 100% for the rest of the year.
• Plans D and M sit in the middle, covering most hospital and medical coinsurance but not everything.
• Some states also offer a high-deductible version of Plan G, with a much lower premium and a deductible you must meet first (the amount is set by Medicare each year).

One term worth knowing: Part B excess charges. A small number of doctors who do not accept Medicare "assignment" may bill up to 15% above the Medicare-approved amount. Plans F and G pay that extra; Plan N does not. How much this matters depends on the doctors in your area, and some states restrict excess charges.

3. Why Plan G Became the Most Popular Choice

Since 2020, people newly eligible for Medicare cannot buy Plan F, which used to be the top seller. Plan G took its place. With Plan G, once you have paid the annual Part B deductible yourself, the plan covers the Part A deductible, hospital coinsurance, the 20% Part B coinsurance, and excess charges. For many people, that means a serious illness brings very few surprise bills — you mainly know your monthly premium and that one deductible.

Plan N is the main budget alternative. Its premiums are often lower, but you pay a copay (up to $20 for some office visits and up to $50 for emergency room visits that do not result in admission), and excess charges are on you. If you rarely see doctors, N can save money. If you see specialists often, G's predictability often wins.

What will you actually pay in premiums? It varies a great deal by state, age, gender, tobacco use, and insurance company. As a rough orientation, a healthy 65-year-old might see Plan G quotes anywhere from about $100 to $300 or more per month — sometimes outside that range in high- or low-cost states. That is exactly why comparing quotes matters: the coverage is identical, so a higher price buys you nothing extra except the company name.

4. One Rule You Cannot Ignore: Medigap and Medicare Advantage Do Not Mix

You cannot use a Medigap policy and a Medicare Advantage plan at the same time. Medigap only works with Original Medicare, and it is illegal for an insurer to sell you a Medigap policy if you plan to keep a Medicare Advantage plan. If you are in a Medicare Advantage plan and want Medigap instead, you would first return to Original Medicare — and outside of certain protected situations, the Medigap insurer may review your health history before accepting you. That is why the timing in the next section matters so much.

5. The Best Time to Buy: Your 6-Month Window

The single most valuable fact in this guide: your Medigap Open Enrollment Period lasts six months, and it begins the month you are both 65 or older and enrolled in Medicare Part B. During this window, insurance companies must sell you any plan they offer, cannot charge you more because of health problems, and cannot make you wait for coverage of pre-existing conditions. In other words, no health questions can be used against you.

Outside that window, in most states an insurer can ask about your health and may decline you or charge more — unless you qualify for a guaranteed issue right. These rights apply in specific situations, for example:

• Your employer group coverage that supplements Medicare is ending.
• Your Medicare Advantage plan leaves Medicare, stops serving your area, or you move out of its service area.
• You tried a Medicare Advantage plan for the first time and switch back to Original Medicare within the allowed trial period.

A handful of states have broader protections or yearly windows, so check your state's rules. The free counselors at your State Health Insurance Assistance Program (SHIP) can explain exactly which rights apply to you.

6. How to Compare and Buy With Confidence

1. Pick the letter first, then shop the price. Decide which plan fits your health and budget, then get quotes for that same letter from several companies.
2. Ask how the premium is priced. Policies are "community-rated" (same price regardless of age), "issue-age-rated" (based on your age when you buy), or "attained-age-rated" (rises as you age). The cheapest quote today is not always the cheapest over ten years.
3. Ask about household discounts and rate history. Some insurers discount couples, and a company with a record of steep increases can erase an early bargain.
4. Use free help. Compare plans at medicare.gov and call your local SHIP office for unbiased, free counseling before you sign anything.

Key Takeaway

Medigap turns Original Medicare's open-ended 20% bills into something predictable, and Plan G is the most complete option for most people who became eligible after 2019. The coverage for each letter is identical no matter which company sells it, so your real job is timing and price: buy during your six-month open enrollment window when no one can turn you down, then compare quotes for the same letter and choose a pricing style that still looks fair at age 75, not just at 65.

This article was written with the help of generative AI.

For general information only, not medical advice.

Consult a qualified professional for your situation.