Medigap plans are supplemental insurance policies sold by private companies that cover out-of-pocket costs left over from Original Medicare. These costs include copayments, coinsurance, and deductibles that Medicare Parts A and B don’t fully pay. You must already have Original Medicare (Parts A and B) before you can buy a Medigap policy.
How Medigap Works With Original Medicare
Original Medicare covers a large share of hospital and medical costs, but it leaves gaps. When you visit a doctor or stay in the hospital, you’re still responsible for deductibles before coverage kicks in and coinsurance on many services. A Medigap policy picks up some or all of those remaining costs, depending on which plan you choose.
Medigap is not the same as Medicare Advantage. Medicare Advantage (Part C) replaces Original Medicare entirely with a bundled plan from a private insurer. Medigap supplements Original Medicare, meaning you keep your Parts A and B coverage and add the Medigap policy on top. You cannot have both a Medigap policy and a Medicare Advantage plan at the same time. One key practical difference: because Medigap works with Original Medicare, you can see any provider nationwide that accepts Medicare. Medicare Advantage plans typically restrict you to a network.
Medigap policies sold after 2005 do not include prescription drug coverage. If you want drug coverage alongside a Medigap plan, you’ll need to enroll in a separate Medicare Part D plan.
The Standardized Plan Options
Medigap plans are standardized by the federal government and labeled with letters: A, B, C, D, F, G, K, L, M, and N. Each letter offers a specific set of benefits that stays the same no matter which insurance company sells the policy. A Plan G from one insurer covers the exact same benefits as a Plan G from another. The only difference between companies is price and customer service.
All plans cover Part A hospital coinsurance and an extra 365 days of hospital coverage after Medicare benefits run out. They also cover the first three pints of blood each year and Part B coinsurance or copayments to varying degrees. Beyond those basics, plans differ in whether they cover the Part A deductible, Part B deductible, Part B excess charges (when a doctor charges more than the Medicare-approved amount), skilled nursing facility coinsurance, and foreign travel emergencies.
Plan G is widely considered the most comprehensive option available to new enrollees. It covers everything except the annual Part B deductible. Plans K and L offer lower premiums but only cover a percentage of certain costs (50% and 75%, respectively) until you hit an annual out-of-pocket limit. Plan N covers most Part B coinsurance but requires small copayments for some office and emergency room visits.
If you live in Massachusetts, Minnesota, or Wisconsin, your state uses its own standardized plan structure rather than the lettered system that applies everywhere else.
Plans C and F Are No Longer Available to Everyone
Plans C and F were historically the most popular Medigap options because they covered the Part B deductible, leaving enrollees with essentially zero out-of-pocket costs. Federal law changed that starting January 1, 2020. If you turned 65 on or after that date, you cannot buy Plan C or Plan F.
People who were eligible for Medicare before January 1, 2020, can still purchase these plans even if they hadn’t enrolled yet. And anyone who already held a Plan C or F policy can keep it. But for most new Medicare beneficiaries, Plan G has become the closest alternative, differing from Plan F only in that it doesn’t cover the Part B deductible.
High-Deductible Versions
Plans F and G are available in high-deductible versions in some states. With a high-deductible plan, you pay lower monthly premiums but must cover all Medicare cost-sharing yourself until you’ve spent a set amount. For 2026, that deductible is $2,950. Once you hit that threshold, the plan pays your covered costs for the rest of the year. This option appeals to people who are relatively healthy, want catastrophic protection, and prefer lower monthly bills.
When to Enroll
Your best window to buy a Medigap policy is during the Medigap Open Enrollment Period, which starts the month you turn 65 and are enrolled in Medicare Part B. This window lasts six months. During this time, insurance companies must sell you any Medigap policy they offer at the standard price, regardless of your health. They cannot charge more or deny coverage because of pre-existing conditions.
Once that six-month window closes, you lose those federal protections. Insurers can use medical underwriting to decide whether to sell you a policy and how much to charge. Some states offer additional protections beyond the federal rules, but in most of the country, buying outside the open enrollment window means you could face higher premiums or be turned down entirely. This makes the timing of your initial enrollment one of the most consequential Medicare decisions you’ll make.
How Premiums Are Priced
Even though Medigap benefits are standardized, premiums vary significantly between insurers and depend on which pricing method a company uses. There are three models:
- Community-rated: Everyone pays the same base premium regardless of age. Your premium won’t increase because you get older, though it can still rise with inflation or other broad factors like where you live or smoking status.
- Issue-age-rated: Your premium is based on your age when you first buy the policy. Someone who enrolls at 65 locks in a lower rate than someone who enrolls at 70. The premium won’t go up due to aging, but inflation and other factors can still cause increases.
- Attained-age-rated: Your premium is based on your current age and goes up as you get older. These plans tend to start with the lowest premiums but can become the most expensive over time.
The pricing method matters more than most people realize. An attained-age policy that looks affordable at 65 could cost substantially more by your mid-70s, while a community-rated policy stays more predictable. Comparing quotes from multiple insurers using the same plan letter is worth the effort, since the coverage is identical and only the price differs.
What Medigap Does Not Cover
Medigap only helps pay for services that Original Medicare already covers. If Medicare doesn’t cover something, Medigap won’t either. That means these policies do not pay for long-term care, dental work (cleanings, fillings, extractions, dentures), routine eye exams for glasses, hearing aids and hearing exams, cosmetic surgery, or massage therapy. Prescription drugs are also excluded from any Medigap policy sold after 2005.
People who need coverage in those areas typically purchase separate standalone plans for dental, vision, hearing, or long-term care insurance alongside their Medigap policy and Part D drug plan.