Medicare Supplement is private insurance that pays for costs Medicare leaves behind
Medicare Supplement insurance (also called Medigap) is a policy you buy from a private insurance company to cover the out-of-pocket costs that Original Medicare does not pay. Original Medicare covers a large share of hospital and doctor bills, but it leaves gaps: you still owe deductibles, copayments, and coinsurance. A Medigap policy fills those gaps by paying some or all of what you owe.
You can only buy Medigap if you have Original Medicare (Part A and Part B). If you have a Medicare Advantage plan instead, you cannot use Medigap — Medicare Advantage already bundles some gap coverage into its own plan structure. Medigap is sold by private insurers, not by Medicare itself, so you shop for plans and pay a monthly premium directly to the insurance company.
Key Takeaways
- Medicare Supplement covers deductibles, copayments, and coinsurance that Original Medicare does not pay, reducing your out-of-pocket costs.
- You can only buy Medigap if you have Original Medicare Part A and Part B, not if you chose a Medicare Advantage plan.
- Medigap plans are standardized by the federal government into lettered plans (A through N), so Plan G from one insurer covers the same things as Plan G from another.
- The best time to buy Medigap is during your six-month open enrollment window starting the month you turn 65 and enroll in Medicare Part B.
- Monthly premiums vary by insurer, age, and location, and some insurers use age-based pricing that increases as you get older.
How Medicare Supplement fills the gaps in Original Medicare
Original Medicare Part A covers hospital stays, skilled nursing care, and hospice, but you pay a deductible ($1,632 in 2024, though this amount changes yearly) before coverage begins. You also pay coinsurance — a percentage of costs — for hospital stays longer than 60 days. Part B covers doctor visits and outpatient care, but you pay a deductible ($240 in 2024) and then 20 percent coinsurance for most services after that.
A Medigap policy steps in and pays those deductibles and coinsurance amounts on your behalf. Which costs it covers depends on which lettered plan you choose. For example, Plan G covers your Part B deductible, your Part A coinsurance, and your Part B coinsurance. Plan N covers most of the same things but leaves you responsible for some copayments at the doctor's office. The federal government defines what each plan covers, so the coverage is identical no matter which insurance company sells it to you.
Medigap does not cover everything. It does not cover dental, vision, hearing aids, or long-term care. It also does not cover prescription drugs — you need Part D for that, which is a separate enrollment. And Medigap does not cover services that Medicare itself does not cover, such as cosmetic surgery or most routine foot care.
The ten standardized Medigap plans and what they cover
The federal government has defined ten Medigap plans, labeled A through N. Each plan covers a different combination of gaps. Plans A, B, D, G, K, L, M, and N are available to people newly turning 65. Plans C and F are closed to new enrollees as of 2020, though people who had them before that date can keep them.
| Plan | Part A Deductible | Part B Deductible | Part B Coinsurance | Hospital Coinsurance |
|---|---|---|---|---|
| Plan A | You pay | You pay | Covered | Covered |
| Plan G | Covered | You pay | Covered | Covered |
| Plan N | Covered | You pay | Covered (except copays) | Covered |
| Plan K | You pay | You pay | Covered (50%) | Covered (50%) |
Plan G and Plan N are the most common choices for people newly turning 65 today. Plan G covers nearly all gaps except your Part B deductible. Plan N covers most gaps but leaves you responsible for small copayments at doctor visits and emergency room visits. Plan A is simpler and less expensive but leaves you paying both the Part A and Part B deductibles. Plans K and L cover only a percentage of costs, making them cheaper but leaving you with more out-of-pocket risk.
When you can buy Medigap and how pricing works
You have a six-month window to buy Medigap without medical underwriting — meaning the insurance company cannot turn you down or charge you more because of your health history. This window starts the first day of the month you turn 65 and enroll in Medicare Part B. If you miss this window, you can still buy Medigap later, but the insurance company may ask health questions, deny you coverage, or charge you a higher premium.
Monthly premiums vary by the plan you choose, the insurance company you buy from, your age, and where you live. A Plan G from one insurer might cost $120 a month, while the same plan from a different insurer costs $160. Some insurers use age-based pricing, which means your premium increases as you get older. Others use community rating, where everyone in your state pays the same price regardless of age. A few use issue-age rating, where your premium is locked to your age when you first buy the plan and does not increase as you age.
You pay your Medigap premium directly to the insurance company each month, separate from your Medicare Part B premium. Your Part B premium goes to Medicare; your Medigap premium goes to the private insurer. Some people find that their total out-of-pocket costs (Medigap premium plus remaining deductibles and copayments) are lower with Medigap than without it, especially if they use healthcare frequently.
Medigap versus Medicare Advantage: which path to choose
When you turn 65, you must choose between two paths: Original Medicare with Medigap, or Medicare Advantage. You cannot have both at the same time. Original Medicare with Medigap gives you the freedom to see any doctor or hospital that accepts Medicare, anywhere in the country. You pay a monthly Medigap premium, but you have predictable out-of-pocket costs because the Medigap plan defines what you owe.
Medicare Advantage is an alternative to Original Medicare offered by private insurers. It typically has a lower or zero monthly premium, but it includes a network of doctors and hospitals you must use (except in emergencies). It also bundles in prescription drug coverage and often includes dental or vision benefits. However, you may face higher copayments and coinsurance when you use care, and you need prior approval from the plan for some services.
If you choose Original Medicare now and later want to switch to Medicare Advantage, you can do so during the annual enrollment period (October 15 to December 7). If you choose Medicare Advantage and later want to switch to Original Medicare with Medigap, you can also switch during that window, but you may face medical underwriting for Medigap if you are past your initial six-month enrollment period.
What to ask your doctor and when to contact Medicare
Before you buy a Medigap plan, ask your current doctors whether they accept Original Medicare. Most do, but some do not. If your doctor does not accept Medicare, Original Medicare with Medigap may not be the right choice for you. You can search for Medicare-accepting doctors on Medicare.gov using the "Find Care Providers" tool.
If you are already on Original Medicare and thinking about adding Medigap, contact your state's Health Insurance Counseling and information Program (HICAP). HICAP is a free, unbiased service that explains your options and helps you compare plans. You can find your state's HICAP by calling 1-800-MEDICARE or visiting Medicare.gov. Do not wait until you have a major health event to buy Medigap — the longer you wait past your six-month window, the harder it becomes to find coverage at a reasonable price.
Frequently Asked Questions
Can I switch Medigap plans after I buy one?
Yes, you can switch to a different Medigap plan at any time, but the new insurer may ask health questions and charge you a higher premium if you have health problems. Your best opportunity to switch without medical underwriting is during the annual open enrollment period (January 1 to March 31), when you can move to any plan offered by any insurer in your state.
Does Medigap cover prescription drugs?
No. Medigap covers only the gaps in Original Medicare's hospital and doctor coverage. You must enroll in a separate Medicare Part D plan to cover prescription drugs. You can enroll in Part D when you first turn 65, or during the annual enrollment period in the fall.
What happens to my Medigap if I move to a different state?
Your Medigap policy may not be honored in your new state, or the same plan may cost more there. Contact your Medigap insurer before you move to ask whether your policy transfers. If it does not, you will need to buy a new Medigap plan in your new state, and you may face medical underwriting if you are past your initial enrollment window.
Is Medigap the same as Medicare Advantage?
No. Medigap is supplemental insurance that works alongside Original Medicare. Medicare Advantage is a replacement for Original Medicare offered by private insurers. You choose one or the other, not both. Medigap gives you more freedom to see any doctor; Medicare Advantage typically costs less but limits you to a network.
What if I cannot afford the Medigap premium?
Some states offer programs that help low-income seniors pay Medigap premiums. Ask your state Medicaid office or your HICAP counselor whether you may have access to. You can also compare plans across insurers — prices vary significantly, and a less comprehensive plan like Plan A or Plan K may cost less than Plan G.