What Is Medigap? What to Know About Medicare Supplement Plans

Medicare Supplement Insurance, or Medigap, is private health insurance that covers “gaps” in Original Medicare coverage. After Medicare pays for its share of covered services, Medigap covers certain out-of-pocket costs, such as copayments, coinsurance and deductibles.

In most states, there are 10 government-standardized Medigap plan types. The plans differ in terms of coverage, premiums and cost-sharing requirements.

Here’s what you need to know about Medicare Supplement Insurance.

How does Medicare Supplement Insurance work?

A Medigap policy can help you cover some or all of these costs for which you’re responsible if you have Medicare Part A and Part B^[0]

• Part A deductible: $1,600 in 2023 for each benefit period.

• Part A inpatient hospital stay coinsurance after day 60: Starting at $400 per day in 2023. (The cost increases after day 90.)

• Part A skilled nursing facility coinsurance after day 20: up to $200 per day in 2023. (You’re responsible for all costs after day 100.)

• Part A hospice care coinsurance and copayments: Up to 5% of the Medicare-approved amount for respite care and up to $5 for each prescription drug.

• Part B deductible: $226 in 2023. (Note: Since 2020, new Medicare members can’t buy any plan that covers the Part B deductible, although existing members may own older plans that do.)

• Part B coinsurance: After the Part B deductible, up to 20% of the Medicare-approved amount for most services and durable medical equipment.

• Part B excess charges, if a provider is permitted to charge more than Medicare’s approved amount and does so.

Without a Medigap policy, you're liable for all of those expenses out of pocket.

Medicare Supplement Insurance can be a useful means to manage your health care costs if you have Original Medicare. (Medigap plans don’t work with Medicare Advantage.) Consider your finances, expected health care expenses, risk tolerance and the Medigap plans available where you live to decide whether Medigap is right for you.

What do Medigap plans cover?

Medigap plans cover certain out-of-pocket health care costs after Medicare Part A or Medicare Part B has paid its share.

Here’s what’s covered by Medigap Plan G, the most comprehensive Medicare Supplement Insurance available to new Medicare members, according to Medicare.gov^[0]

• Part A coinsurance and hospital costs up to an additional 365 days after Medicare benefits are used up.

• Part A deductible.

• Part A hospice care coinsurance or copayment.

• Part B coinsurance or copayment.

• Part B excess charges (if a provider is permitted to charge more than Medicare’s approved amount and does so).

• Blood transfusion (first three pints).

• Skilled nursing facility care coinsurance.

• Medically necessary emergency health care service for the first 60 days when traveling outside the U.S. Deductibles and limitations apply.

There are 10 standardized Medigap plans with varying levels of coverage and cost-sharing, but only eight of the 10 plans are available for purchase by new Medicare members.

New Medicare enrollees are no longer allowed to buy plans that pay for the Medicare Part B deductible. That means if you become eligible for Medicare for the first time after Jan. 1, 2020, you can’t buy Medigap Plan C or Plan F, but the other eight plans are available.

Here are all 10 standardized plans:

(Massachusetts, Minnesota and Wisconsin use their own Medigap plan standards, which differ from the 10-plan standardization system used in the majority of the country.)

» MORE: Compare Medicare Supplement Insurance plans

What Medigap plans don’t cover

Medigap plans sold to new Medicare members do not cover the following:

• Part B deductible. (Since 2020, new Medicare members can’t buy any plan that covers the Part B deductible, although existing members may have older plans that do.)

• Prescription drugs. (If you have Original Medicare, you can enroll in a Medicare Part D plan for prescription drug coverage. Most Medicare Advantage plans include Part D coverage.)

• Long-term care, like the non-skilled care you get in a nursing home.

• Dental care.

• Vision care.

• Private-duty nursing.

How much does Medicare Supplement Insurance cost?

What you’ll pay for Medigap depends on the plan type and health insurer, as well as factors that can include your age, sex, location, tobacco use and health information.

Premiums for a 65-year-old with the least-expensive plans might be as low as $30-$40 per month. For older beneficiaries and plans with greater coverage, premiums can cost hundreds of dollars per month.

In general, high-deductible plans and plans with less coverage, like Plan K and Plan L, have lower premiums. A plan with more comprehensive coverage, such as Plan G, tends to have higher premiums.

Some Medigap plans have other costs in addition to monthly premiums. Here are a few examples of other costs you might pay with certain plans:

• Medigap Plan N has copays for some office and emergency room visits.

• Medigap Plan K and Plan L require you to pay out of pocket for 50% or 25% of most covered services, respectively.

• A high-deductible version of Medigap Plan G requires you to meet a deductible of $2,700 in 2023 before benefits kick in. (High-deductible Medigap Plan F is also available for beneficiaries who qualify for the standard version of Plan F.)

» MORE: Are high-deductible Medigap plans worth it?

When is the best time to sign up for Medicare Supplement Insurance?

Your Medigap open enrollment period, which starts the first month you have Medicare Part B and are 65 years of age or older, is the easiest and least expensive time to enroll in a Medigap plan. The period lasts for six months, during which companies can’t factor your health or medical history into pricing or coverage decisions.

After your Medigap open enrollment period ends, it never happens again, and insurers can charge more or deny coverage for a new plan due to your health status or medical history.

In some states, insurance companies sell Medigap plans to those under 65 who are living with a disability and are eligible for Medicare. You can find more information at your local State Health Insurance Assistance Program, or SHIP.

Can I switch from Medicare Advantage to Medigap?

Yes. If you have Medicare Advantage, there are two periods during the year when you can switch to Original Medicare with a Medigap policy: Medicare open enrollment (Oct. 15 to Dec. 7) and Medicare Advantage open enrollment (Jan. 1 to March 31).

If you're outside of your Medigap open enrollment period when you switch, you'll most likely have to go through medical underwriting. That means insurers can charge higher premiums or refuse to sell you a policy based on your health status or medical history.

There are certain circumstances when you have the right to switch without medical underwriting:

• If you lose your Medicare Advantage coverage, you may have a guaranteed issue right to buy certain Medigap plans.

• If you tried Medicare Advantage and want to go back to Original Medicare with a Medigap policy within the first year, you have a trial right to switch back to certain plans.