Medicare gap coverage fills the costs that Original Medicare leaves you to pay

Original Medicare — Part A (hospital) and Part B (doctor visits) — does not cover everything. You still owe deductibles (the amount you pay before Medicare starts paying), copayments (a fixed amount per visit), and coinsurance (a percentage of the cost). Gap coverage, also called Medigap, is private insurance you buy to cover those out-of-pocket costs that Medicare does not.

When you use a doctor or hospital that accepts Medicare, your Medigap policy pays some or all of what Medicare does not. You pay a monthly premium to the private insurance company selling the plan. The trade-off is that Medigap does not cover services Medicare itself does not cover — like dental, vision, or hearing aids — and it does not cover prescription drugs (that is Part D).

Key Takeaways

  • Medigap is private insurance sold by insurance companies that pays the deductibles, copayments, and coinsurance that Original Medicare leaves you responsible for.
  • There are ten standardized Medigap plans (A, B, D, G, K, L, M, N, and two others), each covering a different combination of out-of-pocket costs, so comparing what each plan covers is the main decision.
  • You can enroll in Medigap during your initial enrollment period when you first turn 65 and sign up for Medicare Part B, or during the annual open enrollment period.
  • Medigap premiums vary by insurance company, age, and location, so getting quotes from multiple insurers is worth the time.
  • If you have a Medicare Advantage plan instead of Original Medicare, you cannot buy Medigap — the two do not work together.

The ten standardized Medigap plans and what they cover

Insurance companies must offer Medigap plans using the same standardized names and benefits across all states (though a few states have different rules). Plan G is the most popular right now because it covers nearly everything Original Medicare does not, except the Part B deductible. Plan N is less expensive but requires you to pay small copayments at the doctor's office and for emergency room visits.

Plan A is the simplest and cheapest option if you want basic coverage. Plans K and L cover a smaller percentage of costs but have lower premiums. Plans D, B, and M are less common because they cover fewer gaps than the more popular options. The Centers for Medicare & Medicaid Services (CMS) publishes a comparison chart showing exactly what each plan covers, which you can find on Medicare.gov.

The plan letter you choose matters much more than the insurance company you choose it from, because the benefits are the same no matter which insurer sells it. The main difference between insurers is the monthly premium they charge for the same plan letter.

When you can sign up for Medigap

Your best window to enroll in Medigap is your initial enrollment period, which starts the month you turn 65 and enroll in Medicare Part B. During this six-month window, insurance companies cannot deny you coverage or charge you more because of health problems — this is called may provide issue. If you miss this window, you can still buy Medigap later, but insurers may refuse to cover you or charge you a higher premium based on your health history.

If you already have Medigap and want to switch plans, you can do so during the annual open enrollment period, which runs from October 15 to December 7 each year. Changes take effect on January 1. Some states also have additional enrollment periods tied to turning 65 or losing other coverage, so check your state's rules on Medicare.gov or by calling 1-800-MEDICARE.

How Medigap premiums work and what affects the cost

You pay a monthly premium directly to the private insurance company, separate from your Medicare Part B premium. The cost varies based on three main factors: which plan letter you choose, which insurance company sells it, and your age and location. Some insurers use community rating (everyone in your area pays the same price regardless of age), while others use age-based rating (your premium rises as you get older).

Premiums also change over time. An insurer might raise rates for all customers, or only for new enrollees. If your premium becomes too high, you can switch to a different insurer selling the same plan letter during the annual open enrollment period, and you will keep your may provide issue protection. Getting quotes from at least three insurers before you enroll is worth doing, because the same plan can cost $50 to $100 more per month depending on the company.

Medigap versus Medicare Advantage: which one lets you use Medigap

If you have Original Medicare (Part A and Part B), you can buy Medigap. If you have Medicare Advantage (Part C), you cannot. The two are different paths: Medicare Advantage is an all-in-one plan run by a private insurance company that covers hospital, doctor, and usually prescription drugs. Medigap is a supplement to Original Medicare that only covers the gaps.

Some people switch from Medicare Advantage to Original Medicare later and then buy Medigap. If you do this outside your initial enrollment period, you may have a limited window to buy Medigap without medical underwriting, depending on your state. Call 1-800-MEDICARE or your state health insurance counselor to understand your options before you switch.

What Medigap does not cover

Medigap covers the gaps in Original Medicare, but it does not cover services that Medicare itself does not cover. Dental work, vision exams, hearing aids, and long-term care are not covered by any Medigap plan. If you need prescription drug coverage, you must enroll in a separate Part D plan.

Medigap also does not cover care outside the United States, though some plans offer limited emergency coverage abroad. If you travel internationally, ask your insurer what is covered before you leave. Some people buy a separate travel insurance policy for trips outside the country.

How to compare plans and choose the right one for you

Start by deciding whether you want maximum coverage (Plan G) or lower premiums with some out-of-pocket costs (Plan N, A, or K). Then get quotes from at least three insurers for the plan letter you chose. Most insurers let you get a quote online or by phone without committing to anything.

Check whether the insurer has good customer service ratings and whether they are financially stable — the National Association of Insurance Commissioners (NAIC) publishes complaint data by company. Also confirm that the plan is available in your state; a few states have different Medigap rules. Once you enroll, you can switch plans or insurers during the annual open enrollment period if you find a better deal.

Frequently Asked Questions

Can I buy Medigap if I already have Medicare Advantage?

No. Medigap and Medicare Advantage cannot be used together. If you have Medicare Advantage and want Medigap, you must first switch back to Original Medicare (Part A and Part B). You can do this during the annual open enrollment period, but you may not have may provide issue protection when you buy Medigap afterward unless your state has special rules.

What happens if I do not buy Medigap during my initial enrollment period?

You can still buy Medigap later, but insurers may deny you coverage or charge you a higher premium based on your health history. Some states have limited windows where you get may provide issue protection even if you enroll late, so check your state's rules. The longer you wait, the more expensive Medigap becomes.

Do I need both Medigap and Part D?

They cover different things. Medigap covers deductibles and copayments for hospital and doctor visits. Part D covers prescription drugs. If you take medications, you need Part D. You can have both at the same time — they work together.

Can I switch Medigap plans if my premium gets too high?

Yes. During the annual open enrollment period (October 15 to December 7), you can switch to a different plan letter or a different insurer. If you switch to a plan with less coverage, you keep your may provide issue protection. If you switch to a plan with more coverage, the insurer may ask about your health.

Does Medigap cover care outside the United States?

Most Medigap plans do not cover routine care abroad, though some offer limited emergency coverage during travel. If you spend time outside the country, ask your insurer what is covered and consider buying a separate travel insurance policy for peace of mind.