Your guide to buying Medicare ​supplemental health insurance

If you decide to enroll in original Medicare, one way you can help pay the extra costs the program doesn’t cover is to buy a supplemental — or Medigap — insurance policy. Here’s what you need to know if you’re in the market for a supplemental policy.

1. Medigap plans are only for original Medicare enrollees

They are sold by private insurance companies but regulated by states and the federal government. Original Medicare pays 80 percent of covered Part B health care services. Medigap insurance typically covers the 20 percent that is your responsibility to pay, along with some other health care costs. In contrast, a Medicare Advantage plan doesn’t allow supplemental insurance, even though it does have various out-of-pocket costs.

2. Medigap isn’t your only supplemental insurance option

You may be eligible for a policy offered by a past or present employer. If you qualify for Medicaid, it too will pick up most out-of-pocket medical costs. About 36 percent of original Medicare enrollees buy a private Medigap plan.

3. You likely have eight to 10 Medigap options

The federal government, not insurers, determines what coverage a Medigap policy provides (except in three states: Massachusetts, Minnesota and Wisconsin). There are 10 federally approved plans, each known by a letter: A, B, C, D, F, G, K, L, M and N. They’re standardized, meaning plans with the same letter name must provide the same basic benefits regardless of the insurer or location.

4. Some options aren’t available to all

Starting in 2020, a cost-cutting move by Congress ended sales of Medigap plans C, F and high-deductible F to individuals newly eligible for Medicare. These plans may still be available if you became eligible for Medicare before Jan. 1, 2020. And if you already have one, you can keep it.

5. Policies are sold by private insurance companies

This means you’ll likely have several choices of plans that have the same letter but are offered by different insurers in your locale. What they charge can vary dramatically.

6. The best time to buy a Medigap plan is (generally) when you first enroll in Medicare

You can buy any Medigap plan available in your state — and insurers can’t turn you down or charge you more due to preexisting health conditions — during the six months after you initially sign up for Medicare Part B. After that, you could be denied or charged higher monthly premiums.

7. Some states set their own enrollment rules

Connecticut and New York let Medicare beneficiaries buy a Medigap plan at any time without being denied. Other states (including California, Idaho, Illinois, Louisiana, Maryland, Missouri, Nevada, Oregon and Washington) let you switch plans at designated times.

8. Different plans have very different prices

For example, a 65-year-old nonsmoking man in Fort Myers, Florida, could pay $64 a month for a Plan K policy or $263 for Plan D. A 65-year-old nonsmoking woman in Wichita, Kansas, might pay $32 a month for a high-deductible Plan G policy versus $455 for a regular Plan G.

9. But shop based on coverage needs, not price

It’s pretty simple: Pay less, get less coverage. For example, plans A and B don’t offer coverage for big-ticket, out-of-pocket costs for stays at skilled nursing facilities. Likewise, high-deductible plans require you to pay thousands up front (up to $2,700 in 2023) before coverage kicks in. Lower-cost policies can be fine if you are relatively healthy, but if something goes wrong, your personal costs can skyrocket. Think long-term.

10. You can get unbiased help in deciding

The best place for more information is your State Health Insurance Assistance Program (SHIP). You can find one in your state at SHIP counselors can give you personalized help choosing a plan. Start early, because these services become increasingly busy toward the end of Medicare open enrollment (Dec. 7 ).