What a Medicare Supplement Plan Does

A Medicare Supplement plan (also called Medigap) is insurance you buy from a private company to cover costs that Original Medicare leaves you responsible for — copayments, coinsurance, and deductibles. Medicare itself pays a portion of your doctor visits and hospital stays, but you still owe money at the point of care. A Medigap policy picks up some or all of those out-of-pocket costs, depending on which plan you choose.

You do not need a Medigap plan to have Medicare coverage. Original Medicare alone is valid insurance. But if you go to the doctor frequently, take multiple medications, or want to know your costs in advance, a Medigap plan can reduce surprises and lower your total spending.

Medigap is different from Medicare Advantage (Part C), which is an alternative way to receive Medicare benefits through a private plan. If you have Original Medicare, you can add a Medigap plan. If you have Medicare Advantage, you cannot.

Key Takeaways

  • Medigap plans are standardized by the federal government, so Plan G from one company covers the same things as Plan G from another — the only difference is price.
  • The ten available plans range from Plan A (lowest cost, lowest coverage) to Plan N (higher cost, more coverage), and your choice depends on how much you use healthcare and what you can afford monthly.
  • You have a six-month window starting the month you turn 65 and enroll in Medicare Part B to buy a Medigap plan without being denied or charged more for pre-existing conditions.
  • Outside that window, insurance companies can refuse to sell you a plan or charge you extra based on your health history, so timing your enrollment matters.
  • Comparing plans means looking at the monthly premium, the deductible you pay before coverage starts, and which specific costs the plan covers — not just picking the cheapest option.

The Ten Standardized Medigap Plans and What They Cover

The federal government defines ten Medigap plans, labeled A through N. Each plan covers a fixed set of costs. Plan A is the most basic and least expensive. Plan G covers more costs and costs more per month. Plan N is somewhere in the middle on both price and coverage. Insurance companies cannot change what each plan covers — they can only set the price.

The most popular plans are A, G, and N. Plan A covers the Part B deductible, copayments for doctor visits and hospital stays, and blood transfusions. Plan G covers everything Plan A does, plus the Part B deductible and some preventive care costs. Plan N covers similar ground but leaves you responsible for some copayments at the doctor's office and urgent care center.

Plans D, H, I, and J are no longer sold to people new to Medicare, though people who already have them can keep them. Plans K and L are also available but less common. The best way to see what each plan covers is to use the official Medicare plan comparison tool at Medicare.gov, which shows side-by-side what each plan pays for.

When You Can Enroll Without Restrictions

The six-month open enrollment period for Medigap starts the first day of the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies must sell you any Medigap plan you want at their standard price. They cannot refuse you, charge you more, or exclude coverage for pre-existing conditions.

If you miss this window, you can still buy a Medigap plan later, but the rules change. Insurance companies can deny you coverage entirely, charge you a higher premium based on your health history, or exclude certain conditions from coverage for up to six months. Some states have additional protections that extend or modify these rules, so check with your state insurance commissioner's office if you enroll late.

The safest approach is to enroll in a Medigap plan during your open enrollment period, even if you are not sure you need it yet. You can always switch to a different plan later if your needs change.

How to Compare Plans by Cost and Coverage

Comparing Medigap plans means looking at three numbers: the monthly premium, the annual deductible, and what the plan actually covers. A plan with a low premium might have a high deductible, meaning you pay more out of pocket before the plan starts paying. A plan with no deductible might have a higher monthly cost.

Use the Medicare plan comparison tool to list all available plans in your area, sorted by premium. Then read what each plan covers — specifically, whether it covers the Part B deductible, how much you pay for doctor visits, and whether it covers prescription drugs (it does not; that is Part D, which you buy separately). Write down the total you would pay in a typical year: monthly premiums plus the deductible plus any copayments you expect to make based on how often you see doctors.

Price varies by location and insurance company. The same Plan G might cost $120 a month in one county and $180 in another. Get quotes from at least three companies before deciding. Many people find that calling the insurance company directly or using their website is faster than comparing on Medicare.gov, though both methods show the same plans.

Prescription Drug Coverage and Medigap

Medigap plans do not cover prescription drugs. If you take medications regularly, you need to enroll in a separate Part D plan (prescription drug coverage) through Medicare. You choose a Part D plan during the same enrollment window as your Medigap plan, and you can switch Part D plans every year in the fall, even if you keep the same Medigap plan.

Part D plans vary widely in which drugs they cover and how much you pay. If you take expensive medications, spend time on the Medicare website or call your pharmacy to see which Part D plans cover your specific drugs at the lowest cost. Some Part D plans are free or very cheap if you take common, inexpensive medications; others cost more but cover expensive specialty drugs.

If you do not enroll in Part D when you first become may be able to access, you may pay a penalty for every month you delay, even if you do not take any medications now. The penalty is added to your Part D premium for as long as you have Medicare.

What Happens When You Switch Plans

You can switch to a different Medigap plan at any time, but the rules depend on whether you are still in your open enrollment period. During the first six months after you turn 65 and enroll in Part B, you can switch plans without being denied or charged more. After that window closes, insurance companies can refuse to sell you a new plan or charge you extra based on your health.

Some states allow you to switch plans once a year without undergoing medical underwriting (a review of your health history), but this varies. Check with your state insurance commissioner's office to see what protections explore where you live.

If you want to switch plans, contact the new insurance company directly. They will tell you whether they will sell you the plan and what your premium will be. Do not cancel your current plan until the new one is active, so you do not have a gap in coverage.

Questions to Ask Your Doctor or Insurance Agent

Before you choose a plan, ask your primary care doctor how often you typically see specialists, how many medications you take, and whether you expect any major procedures in the next year. This helps you estimate how much you will actually spend out of pocket and whether a plan with higher coverage is worth the extra monthly cost.

Ask your insurance agent or the insurance company directly: What is the total I will pay in a year if I see my doctor once a month and fill four prescriptions? Does this plan cover my current doctors and pharmacy? What happens if I need emergency care while traveling? Can I switch plans next year if my needs change?

If you are unsure whether you need a Medigap plan at all, ask Medicare directly by calling 1-800-MEDICARE. They can explain what Original Medicare covers and what you would pay without a supplement plan.

Frequently Asked Questions

Can I have both a Medigap plan and Medicare Advantage?

No. You choose either Original Medicare with a Medigap plan, or Medicare Advantage. If you have Medicare Advantage and want to switch to Original Medicare with Medigap, you can do so during the annual open enrollment period (October 15 to December 7), and your Medigap open enrollment period restarts when you switch.

What if I turn 65 but do not enroll in Medicare right away?

Your Medigap open enrollment period starts when you enroll in Medicare Part B, not when you turn 65. If you delay enrolling in Medicare, your open enrollment window starts later. However, if you have employer health insurance and delay Medicare enrollment, you may have special protections — ask your employer's benefits office.

Do I have to buy a Medigap plan?

No. Original Medicare alone is valid insurance. Many people do fine without a Medigap plan, especially if they are healthy and do not see doctors often. But if you go to the doctor frequently or want to know your costs in advance, a Medigap plan usually saves money over time.

Can my Medigap premium go up?

Yes. Insurance companies can raise premiums for everyone in a plan, or they can raise your premium specifically based on your age. The rules vary by state and insurance company. Ask the company what their premium history has been and whether they use age-based pricing.

What if I cannot afford any Medigap plan?

Some states offer programs for low-income seniors that help pay Medigap premiums. Contact your state Medicaid office or your local Area Agency on Aging to ask whether you may have access to. You can also choose Original Medicare without a supplement plan and use community health centers for routine care, though your out-of-pocket costs may be higher.