Nearly one in four Medicare beneficiaries faces out-of-pocket healthcare costs exceeding $5,000 per year, according to KFF research. Supplemental plans exist to close the financial gaps that Original Medicare leaves behind, and choosing the right one can mean the difference between predictable healthcare expenses and financial uncertainty in retirement. This guide explains the major types of supplemental coverage, how they work, and how to determine which option fits your needs.
What Are Supplemental Plans?
In the context of Medicare, supplemental plans are insurance policies that cover costs Original Medicare does not fully pay. Original Medicare (Parts A and B) requires beneficiaries to pay deductibles, coinsurance, and copays that have no annual cap. A single hospital stay can trigger a $1,676 Part A deductible in 2026, and outpatient services carry 20 percent coinsurance with no limit on how much that 20 percent can add up to. Supplemental plans absorb some or all of these costs.
The most common type of supplemental plan is a Medigap policy, also called Medicare Supplement Insurance. Medigap plans are sold by private insurers but standardized by the federal government into plan letters A through N. Each letter covers a specific set of benefits, and those benefits are identical regardless of the carrier. Other forms of supplemental coverage include employer or retiree group plans, Medicaid (for dual-eligible beneficiaries), and Medicare Advantage (which is technically an alternative to Original Medicare rather than a supplement). For more on the policy framework, visit our healthcare policy guide.
The Medigap Plan Letters
Ten standardized Medigap plans are available in most states: A, B, C, D, F, G, K, L, M, and N. Plans C and F are only available to beneficiaries who became Medicare-eligible before January 1, 2020. Among currently available options, Plan G and Plan N are the most popular. Plan G covers all Medicare cost-sharing except the annual Part B deductible of $257. Plan N covers most of the same costs but requires copays of up to $20 for office visits and up to $50 for ER visits that do not result in admission.
Plans K and L offer lower premiums but cover only 50 percent (Plan K) or 75 percent (Plan L) of certain benefits until you reach an annual out-of-pocket limit. Plan A covers the basics but omits the Part A deductible and foreign travel emergency coverage. For a full breakdown of what each plan covers, our Medicare Supplement plan comparison lays out the differences in detail.
Cost of Supplemental Plans
Monthly premiums for Medigap plans vary based on your age, location, gender, tobacco use, and the insurance company. In 2026, typical premium ranges are: Plan G at $120 to $300 per month, Plan N at $80 to $220, Plan F at $150 to $350, and Plans K and L at $40 to $130. These premiums are in addition to your Part B premium of $185 per month.
The total annual cost of a supplemental plan includes your monthly premium plus any remaining out-of-pocket costs. For Plan G, that total is your premium multiplied by 12 plus the $257 Part B deductible. For Plan N, add the deductible plus any office visit and ER copays. When comparing the true cost of supplemental plans, always calculate the full-year expense rather than looking at premiums alone. Our Medicare Supplement plans cost article walks through this calculation step by step.
How Supplemental Plans Differ From Medicare Advantage
A common point of confusion is the difference between supplemental plans and Medicare Advantage. Supplemental plans (Medigap) work alongside Original Medicare. You keep Parts A and B, and the supplement covers the remaining costs. Medicare Advantage (Part C) replaces Original Medicare with a private plan that manages all your benefits through a provider network.
You cannot have both a Medigap plan and a Medicare Advantage plan simultaneously. If you choose Medicare Advantage, your supplement becomes redundant and the insurer should stop charging you. Medicare Advantage often includes drug, dental, and vision coverage but may impose network restrictions and prior authorization requirements. Medigap gives you unrestricted provider access but does not cover drugs, dental, or vision. For a thorough side-by-side analysis, see our Medigap vs Medicare Advantage comparison.
Who Needs Supplemental Coverage
Most Medicare beneficiaries benefit from some form of supplemental coverage. Without it, you face unlimited out-of-pocket exposure for Medicare-covered services. Individuals with chronic conditions, those who see specialists frequently, and anyone who wants financial predictability in retirement should strongly consider a Medigap plan. Even relatively healthy beneficiaries face the risk of an unexpected diagnosis or accident that could result in substantial cost-sharing.
Beneficiaries who may not need Medigap include those who qualify for Medicaid (which covers Medicare cost-sharing), those with comprehensive employer or retiree benefits, and those who choose Medicare Advantage (which includes an annual out-of-pocket maximum). The key question is whether you have another source of financial protection against Medicare’s open-ended cost-sharing. If the answer is no, supplemental coverage is important. Learn more about coverage options in our healthcare costs guide.
Enrollment Timing
The most important enrollment window for Medigap is your Open Enrollment Period, which lasts six months beginning the first day of the month you turn 65 and are enrolled in Part B. During this period, insurers cannot deny you coverage, charge higher premiums based on health conditions, or impose waiting periods for pre-existing conditions. This guaranteed-issue right is available only once under federal law.
After your Open Enrollment Period expires, insurers can use medical underwriting. You could be denied coverage entirely, charged higher premiums, or subjected to waiting periods. Some states, including New York, Connecticut, Massachusetts, and California, offer additional protections such as continuous open enrollment or guaranteed-issue rights in specific situations. Understanding your state’s rules is essential when planning your enrollment in supplemental plans.
Choosing the Right Supplemental Plan
Start by assessing your healthcare needs and financial tolerance for risk. If you want maximum protection and minimal out-of-pocket costs, Plan G is the standard choice for new enrollees. If you are comfortable with small copays and want a lower premium, Plan N offers a strong balance. If budget is your primary concern and you can handle a higher share of costs, Plans K or L may work.
Once you select a plan letter, compare carriers. Since benefits are standardized, the best carrier is the one offering a competitive premium, strong financial ratings (AM Best A- or higher), a history of moderate rate increases, and any discounts you qualify for. Request quotes from at least five insurers. Your state insurance department and the Medicare.gov plan finder are both useful starting points. For state-specific guidance, see our articles on plans in Colorado, Kansas, and Delaware.
Frequently Asked Questions
Do supplemental plans cover prescription drugs?
Medigap plans sold after 2006 do not cover prescription drugs. You need a separate Medicare Part D plan for drug coverage. Most Medicare Advantage plans include Part D drug coverage as part of the plan. If you choose Medigap, enroll in Part D during your Initial Enrollment Period to avoid late enrollment penalties.
Can I change my supplemental plan later?
You can switch Medigap plans at any time, but outside your initial Open Enrollment Period you may need to pass medical underwriting. Some states offer annual windows for switching without underwriting. Medicare Advantage plans can be changed during the Annual Enrollment Period each fall.
How much do supplemental plans save me?
For a beneficiary with a significant health event, Medigap can save thousands of dollars in a single year. A 10-day hospital stay under Original Medicare without a supplement could cost over $2,000 in Part A cost-sharing alone. With Plan G, your entire annual cost-sharing for covered services is limited to $257.
Are supplemental plans tax deductible?
Medigap premiums may be tax deductible as a medical expense if your total medical expenses exceed 7.5 percent of your adjusted gross income. Consult a tax professional for guidance specific to your situation.
Protecting Your Finances
Supplemental plans are fundamentally about financial protection. They transform Medicare’s open-ended cost-sharing into a predictable expense. Whether you choose a comprehensive plan like Plan G, a budget-friendly option like Plan N, or a Medicare Advantage plan with an out-of-pocket cap, having some form of supplemental coverage reduces the financial risk that comes with aging. Enroll during your guaranteed-issue window, compare your options carefully, and choose coverage that matches both your health needs and your budget. Explore the full range of Medigap plans to find the right fit.