Medicare Supplement Plans Fill the Gaps That Original Medicare Leaves
Medicare Supplement insurance, also called Medigap, is a policy sold by private insurance companies that pays for costs that Original Medicare (Parts A and B) does not cover. Original Medicare leaves you responsible for deductibles, copayments, and coinsurance — the amounts you owe when you use a doctor or hospital. A Medigap plan picks up some or all of those out-of-pocket costs, depending on which plan you choose.
Medigap is different from Medicare Advantage (Part C), which is an alternative way to get Medicare benefits through a private plan. With Medigap, you keep Original Medicare and add a supplement on top. You can see any doctor or hospital that accepts Medicare, and there are no networks to navigate.
You buy Medigap directly from an insurance company, not from Medicare. The monthly premium comes out of your pocket, separate from your Medicare Part B premium. The amount you pay depends on your age, where you live, which plan letter you choose (A through N), and the insurance company you pick.
Key Takeaways
- Medigap covers deductibles, copayments, and coinsurance that Original Medicare does not pay, but it does not cover dental, vision, hearing, or prescription drugs.
- Plans are standardized by letter (A through N), so Plan G from one company covers the same things as Plan G from another — only the price differs.
- You can enroll during your initial Medicare enrollment window or during the annual open enrollment period, but waiting can cost you more if you have health problems.
- Some states allow insurance companies to charge based on your health history; others do not, so your location affects what you will pay.
- You must have Original Medicare Part A and Part B to buy Medigap; you cannot use it with Medicare Advantage.
The Ten Standardized Medigap Plans and What Each Covers
Insurance companies cannot create their own Medigap plans. Instead, they must offer plans labeled A through N, and each letter has a set of benefits defined by Medicare. Plan A is the most basic and least expensive. Plan G and Plan N are the most popular because they cover most out-of-pocket costs without being the most expensive option. Plan F was once the most comprehensive, but Medicare stopped selling it to new beneficiaries in 2020.
The chart below shows which costs each plan covers. An "X" means the plan pays that cost; a blank means you pay it yourself.
| Cost | Plan A | Plan G | Plan N |
|---|---|---|---|
| Part A deductible | X | X | |
| Part B deductible | |||
| Part B copayments and coinsurance | X | X | X* |
| Hospital coinsurance | X | X | X |
| Blood (first three pints) | X | X | X |
| Skilled nursing facility coinsurance | X | X | |
| Part A hospice coinsurance | X | X | X |
| Foreign travel emergency care | X | X |
*Plan N charges a copayment for some doctor visits and urgent care, and you pay the Part B deductible yourself. This is why Plan N costs less than Plan G but requires you to pay more when you use care.
What Medigap Does Not Cover
Medigap covers only the gaps in Original Medicare. It does not cover services that Original Medicare itself does not cover. Dental work, eye exams, eyeglasses, hearing aids, and routine hearing tests are not covered by any Medigap plan. Long-term care in a nursing home or at home is not covered. Prescription drugs are not covered by Medigap — you need a separate Part D plan for that.
Medigap also does not cover care you receive outside the United States, except for limited emergency care during travel (and only some plans cover that). If you travel abroad for extended periods, you would need a separate travel insurance policy.
How Much Medigap Costs and Why Prices Vary
Medigap premiums vary widely based on three main factors: your age, your location, and which insurance company you choose. A Plan G policy might cost $120 per month in one state and $200 in another. The same plan from two different companies in the same state can differ by $50 or more per month.
Insurance companies use one of three pricing methods. Age-attained pricing means your premium goes up as you get older. Issue-age pricing means your premium is based on your age when you first buy the plan and does not increase with age (though it may increase for other reasons). Community rating means everyone in your state pays the same premium regardless of age. Your state determines which method companies can use, so where you live affects what you pay.
In some states, insurance companies can charge more if you have existing health conditions. In other states, they cannot. This is called medical underwriting. If you have a history of heart disease or diabetes, you may pay significantly more in a state that allows underwriting, or you may pay the same as everyone else in a state that does not.
When You Can Enroll in Medigap and What Happens If You Wait
You have the strongest protection if you enroll in Medigap during your Medigap open enrollment period, which lasts six months and starts the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies must sell you any plan you want at the lowest price they offer, regardless of your health. They cannot turn you down or charge you more because of health problems.
If you miss this window, you can still buy Medigap during the annual open enrollment period, which runs from October 15 to December 7 each year. Outside these windows, insurance companies can refuse to sell you a plan or charge you more based on your health history — depending on your state's rules. Some states offer additional enrollment periods if you lose coverage or move, but these vary by location.
Waiting to enroll can be expensive. If you have high blood pressure, arthritis, or other chronic conditions, an insurance company in a state that allows underwriting may charge you 50% to 100% more than someone without those conditions. The longer you wait after your initial enrollment period ends, the more likely you are to face these higher rates.
How to Compare Plans and Choose the Right One
Start by deciding which plan letter makes sense for your situation. Plan A is cheapest but leaves you paying the Part A deductible. Plan G covers almost everything except the Part B deductible, which is $240 in 2024 (this amount changes yearly). Plan N is cheaper than Plan G but requires copayments for some doctor visits. If you see doctors frequently or have high medical costs, Plan G or Plan N usually saves you money despite the higher premium. If you rarely see a doctor, Plan A might be enough.
Once you have chosen a plan letter, compare prices from at least three insurance companies in your state. Medicare.gov has a tool that shows plans available in your area and their premiums. You can also contact companies directly or work with a licensed insurance agent who represents multiple companies. Agents do not charge you — they are paid by the insurance company — but verify that an agent is licensed before sharing personal information.
Do not choose based on premium alone. A plan $20 cheaper per month might have a higher deductible or copayments that cost you more in the long run. Look at the total cost: premium plus the out-of-pocket costs you are likely to face based on your health and how often you use care.
Switching Plans and What Happens to Your Coverage
You can switch from one Medigap plan to another during the annual open enrollment period (October 15 to December 7). You can also switch at any time in some states, though the new company may charge you more or deny coverage based on health conditions if you are outside an enrollment window.
If you switch plans, your old coverage ends and your new coverage begins on the first day of the following month. There is usually no gap, but confirm the effective date with your new insurance company before your old plan ends. If you are switching because your current company is raising rates, shop early — waiting until December to switch means you may pay the higher rate for several months before the new plan takes effect.
If you switch from Medigap to Medicare Advantage, you cannot switch back to Medigap later without going through medical underwriting in most states. This is a one-way door in many cases, so understand the differences before you make the change.
Frequently Asked Questions
Do I need Medigap if I have Medicare Advantage instead?
No. Medicare Advantage (Part C) is a complete alternative to Original Medicare, and you cannot use Medigap with it. Medicare Advantage includes prescription drug coverage and often covers dental and vision, but it uses networks and requires prior authorization for some care. Medigap works only with Original Medicare.
Will my Medigap premium increase every year?
Yes, in most cases. Premiums increase due to inflation, rising healthcare costs, and sometimes your age (depending on the pricing method your company uses). Some companies raise rates more than others, which is why comparing prices every year during open enrollment makes sense. You might find a cheaper plan from a different company.
What happens to my Medigap coverage if I move to another state?
Your current plan ends when you move. You will need to enroll in a new Medigap plan in your new state, because plans and prices are state-specific. Some states allow you to enroll without medical underwriting if you move, but this varies. Contact your new state's insurance commissioner's office or Medicare to learn your options before you move.
Can I use Medigap coverage outside the United States?
Most Medigap plans do not cover care outside the U.S. Only some plans (C, D, E, F, G, H, I, J, M, and N) cover limited emergency care during foreign travel, and only up to a certain amount. If you travel abroad regularly, ask your insurance company about coverage limits and consider a separate travel insurance policy.
What is the difference between Medigap Plan G and Plan N?
Plan G covers the Part B deductible; Plan N does not. Plan N also charges copayments for some doctor visits and urgent care, while Plan G does not. Plan N costs less per month, but you pay more when you use care. Plan G costs more per month but has lower out-of-pocket costs when you see doctors. The right choice depends on how often you expect to use healthcare.