Medicare Supplement (Medigap): Comprehensive Guide (2026)

Medicare Supplement insurance?widely known as "Medigap"?is a type of private health insurance explicitly designed to fill the costly financial "gaps" left behind by Original Medicare. While the federal government provides your primary coverage, it is not designed to pay for everything, leaving you exposed to significant out-of-pocket expenses.

Recognizing this financial risk, roughly 25% of all Medicare beneficiaries (approximately 15 million Americans) choose to safeguard their retirement savings by purchasing a Medigap plan.

To protect consumers, Medigap plans are strictly standardized by federal law. In most states, there are 10 distinct, standardized plan options. This standardization means that the coverage benefits of a specific plan type are legally mandated to be identical, regardless of which private health insurance company sells it to you. For instance, Plan G from Company A offers the exact same medical benefits as Plan G from Company B. Therefore, when you are shopping for a Medigap policy, your decision ultimately comes down to two factors: the monthly premium price and the customer service reputation of the insurer.

While all policies within a specific letter category offer the same core benefits, some insurers may throw in minor extra perks (like gym memberships) to attract business. It is important to note that if you live in Massachusetts, Minnesota, or Wisconsin, your state government standardizes Medigap policies differently than the rest of the country.

What exactly are the "gaps" in Original Medicare?

If you have reviewed our foundational guide, What is Medicare?, you know that Original Medicare is divided into two parts: Part A (Hospital Insurance) and Part B (Medical Insurance).

Crucially, Original Medicare is only designed to help cover the costs of your medical and hospital services?it does not pay the bill in full. Under both Part A and Part B, you are personally responsible for paying deductibles, flat-fee copays, and percentage-based coinsurance. These cumulative out-of-pocket costs are the very "gaps" that a Medigap policy is built to cover.

Below is a stark summary of the financial liabilities you face if you rely solely on Original Medicare without supplemental protection.

What are the different types of Medicare Supplement (Medigap) plans?

Currently, the standard Medigap market offers 10 different lettered plans: Plans A, B, C, D, F, G, K, L, M, and N. Each specific letter dictates a different, standardized level of financial protection.

Because Medigap plans are identical by letter across the industry, the only differences you will experience between Company A's Plan G and Company B's Plan G are the premium you pay and how smoothly the company handles your billing.

It is critical to note a recent change in federal law regarding the Medicare Part B deductible. Effective January 1, 2020, any Medigap plan that pays the Part B deductible on your behalf?specifically Plans C and F?can no longer be legally sold to anyone newly eligible for Medicare. If you became eligible for Medicare before 2020, you are grandfathered in and may still purchase Plan C or Plan F. Additionally, Plans E, H, I, and J have been discontinued for new buyers for years, though beneficiaries who already hold these policies are allowed to keep them.

The table below illustrates the varying coverage levels. Plan A provides the bare minimum required coverage, while Plans F and G act as the "cadillac" options, absorbing nearly all of your medical financial risk.

Notes: Y = Yes, ? = Not Covered
* Plans F and G also feature a "high-deductible" variant in select states. With this structure, you must pay out-of-pocket for all Medicare-covered costs until you hit a $2,700 deductible (in 2026) before the Medigap policy pays a dime. (As a reminder, Plans C and F are unavailable to anyone who became eligible for Medicare on or after January 1, 2020.)

** For Plans K and L, once your out-of-pocket spending reaches the annual limit and you have paid your yearly Part B deductible, the Medigap plan will completely cover 100% of your approved services for the remainder of the calendar year.

*** Plan N is highly popular because it pays 100% of your Part B coinsurance, but it does require you to pay small copays: up to $20 for typical office visits, and up to $50 for emergency room visits that do not result in a formal hospital admission.

High Deductible and Cost-Share Medigap Plans

Plan F and Plan G offer the ultimate peace of mind. Because they cover virtually 100% of the "gaps" in Original Medicare, your healthcare costs are effectively capped at whatever you pay for the monthly premium. However, because the insurance company takes on almost all the risk, these plans carry the highest monthly price tags.

To make these comprehensive plans more affordable, some states offer "high-deductible" versions of Plans F and G. If you choose this route, you agree to pay for all your copays, coinsurance, and deductibles up to a threshold of $2,700 before the Medigap policy steps in to help. In exchange for taking on this initial financial burden, you are rewarded with a significantly lower monthly premium.

Plans K and L operate on a "cost-sharing" model, meaning they only pay a percentage of your out-of-pocket costs. However, they include a strict safety net: once your personal spending hits the annual limit ($6,940 for K; $3,470 for L) plus your Part B deductible ($283 in 2026), the plan pays 100% of your covered costs for the rest of the year. Like the high-deductible options, taking on more upfront risk earns you a lower monthly premium.

Should I enroll in a Medicare Supplement (Medigap) plan?

Before diving into specific Medigap letters, you must make a foundational decision: do you want to stick with Original Medicare (managed by the federal government), or do you prefer to privatize your care through a Medicare Advantage plan?

Medicare Advantage (Part C) acts as a bundled, "all-in-one" substitute for Original Medicare. Administered by private insurers, these plans merge your hospital and medical coverage and frequently add in Part D prescription drug benefits, along with extras like routine dental and vision care.

The choice to remain on Original Medicare almost always hinges on the freedom to choose your doctor. Original Medicare allows you to visit any doctor or hospital in the entire country that accepts Medicare, with zero network restrictions or referral requirements. To explore this core difference further, read our guide on Medicare Advantage vs. Original Medicare.

If you demand the boundless network freedom of Original Medicare, purchasing a Medigap plan is highly recommended. The core benefits include:

• Nationwide coverage: Because Original Medicare acts as your primary insurance, your Medigap policy must be accepted by any doctor, specialist, or facility nationwide that takes Medicare. You are never restricted to a local network.
• Ironclad cost management: Medigap transforms unpredictable, terrifying medical bills into a predictable, manageable monthly premium. For instance, if a major surgery results in a massive Part B bill, Original Medicare demands you pay 20% of the cost. Without Medigap, that 20% could bankrupt you. With a Medigap plan that covers Part B coinsurance, the insurance company pays that massive bill, saving your retirement. This makes Medigap essential for individuals with chronic illnesses who face frequent medical interventions.
• Guaranteed renewable status: Once you have a Medigap policy, the insurance company is legally forbidden from canceling your coverage due to declining health. As long as you dutifully pay your premium, your coverage is locked in for life.

What Supplement (Medigap) plan should I enroll in?

Choosing the right Medigap letter requires an honest assessment of your health trajectory and your monthly budget. Because Medigap is fundamentally an exercise in risk management, you must decide how much financial risk you want to offload to the insurance company.

When comparing plans, weigh these two competing factors:

• Monthly Premium: Can your fixed retirement income comfortably sustain the monthly premium year after year? If you stop paying, you lose the coverage.
• Usage of Medical Services: Are you frequently at the doctor's office? Do you have hereditary conditions that suggest expensive medical care is in your future? If you use the healthcare system heavily, paying a higher premium for a comprehensive plan like Plan G is almost always cheaper in the long run.

Here is a practical example: Let's assume a Plan G policy costs you $150 a month ($1,800 annually). You must also pay your standard Part B premium to the government, which is $202.90 a month in 2026 ($1,979 annually). Because Plan G covers literally everything except the annual Part B deductible ($283), your absolute maximum healthcare expenditure for the entire year is capped at $4,005 ($1,800 + $1,979 + $283). If you anticipate that a sudden illness could result in medical bills far exceeding $4,000, paying the premiums for Plan G is a highly strategic financial decision.

You must apply this logic to the other lettered plans, finding the "sweet spot" between the premiums you pay and the out-of-pocket risk you are willing to stomach. For further insight, review our report on the most popular Medigap plans to see how your peers are navigating this decision.

When can I enroll in a Supplement (Medigap) plan?

Legally, if you are eligible for Medicare, you have the right to apply for a Medigap plan on any day of the year. However, there is a dangerous catch: outside of a few highly specific windows, federal law does not require private insurance companies to actually sell you a policy.

If you apply outside of these protected windows, insurance companies will subject you to rigorous "medical underwriting." They will scrutinize your medical history, and they have the full legal right to flatly deny your application, charge you an exorbitant premium, or enforce a grueling 6-month waiting period before they will cover your pre-existing conditions.

Medicare Supplement Open Enrollment Period (MS-OEP)

The golden exception to this harsh reality is your MS-OEP. This is a one-time, non-repeatable 6-month window that triggers the exact month your Medicare Part B coverage goes active.

During these critical six months, federal "guaranteed issue" laws force Medigap companies to:

1. Sell you any Medigap policy they offer, completely bypassing medical underwriting.
2. Accept you regardless of any current or past health nightmares.
3. Charge you the exact same premium they charge a perfectly healthy person your age.

For most retirees, this MS-OEP window opens exactly when they turn 65. However, if you continue working and receive qualifying health insurance through your employer, you can safely delay Part B. Your 6-month MS-OEP will then trigger later, the moment you finally activate Part B.

Furthermore, if you had at least 6 months of continuous "creditable coverage" (like an employer health plan) right before your MS-OEP, and you did not have a lapse in coverage exceeding 63 days, Medigap companies are legally forbidden from imposing any waiting periods for your pre-existing conditions.

We cannot stress this enough: your MS-OEP happens only once. If you let it expire without buying a policy, you surrender your guaranteed right to purchase Medigap. Buying later means facing the very real threat of denial. While a few states enforce additional consumer protections, the vast majority of Americans must act during this 6-month window to secure their financial future.

Final Words

If you value the freedom to choose your own doctors across the nation, coupling Original Medicare with a robust Medigap policy is the gold standard for your healthcare. While you have 10 standardized plans to choose from (provided you were eligible for Medicare before 2020), the most crucial factor is timing. Failing to purchase your policy during your one-time Medicare Supplement Open Enrollment Period could leave you exposed to devastating medical bills you cannot afford.