Supplemental Medicare plans: what they cover and how to choose

In 2026, the Part A inpatient deductible is $1,736 per benefit period, not per year. Two separate hospitalizations can each trigger the full deductible. From days 61 to 90 of a hospital stay, coinsurance runs $434 per day. If you exhaust the standard 90 days, each lifetime reserve day costs $868, and there are only 60 reserve days over your entire lifetime.

For skilled nursing facility (SNF) care, days 1 to 20 are fully covered after a qualifying hospital stay, but days 21 to 100 carry a $217 per day coinsurance charge in 2026. After day 100, Medicare pays nothing.

On the Part B side, in 2026 the standard monthly premium is $202.90 and the annual deductible is $283. After that deductible, Medicare covers 80% of the approved amount and you owe 20%, with no annual ceiling on that 20% exposure. If your provider does not accept Medicare assignment, they may charge up to 15% above the Medicare-approved amount; some states ban those excess charges entirely.

Prescription drugs are not covered by Original Medicare at all without a Part D (prescription drug) plan attached.

In short: the gaps in Original Medicare are real and potentially large; supplemental coverage is how most beneficiaries manage them.

Medigap, also called Medicare Supplement Insurance, is private insurance that works alongside Original Medicare. When Medicare processes a claim first, Medigap pays some or all of what remains, depending on which standardized plan letter you hold.

Plans are labeled by letter (A, B, C, D, F, G, K, L, M, N, and the high-deductible variants). The coverage each letter provides is set federally, so a Plan G from one insurer covers the same benefits as a Plan G from any other insurer. What varies is the premium. Plans F and C are no longer available to beneficiaries who became eligible after January 1, 2020.

Plan G is currently the most comprehensive option available to new enrollees. It covers the Part A deductible, Part A coinsurance, Part B coinsurance, excess charges, and foreign travel emergency care (to policy limits). The only thing it does not cover is the Part B deductible. The high-deductible version of Plan G carries a lower monthly premium in exchange for paying the first $2,950 in 2026 before coverage kicks in.

Plan N also covers Part A coinsurance and the Part B coinsurance for most services, but it does not cover excess charges and uses copays for some office visits and emergency room visits.

The guaranteed-issue window

The single most important timing fact in Medigap is the open enrollment window: six months, starting the month you turn 65 and are enrolled in Part B. During this window, no insurer may use medical underwriting, deny coverage, or charge a higher premium because of health status. Outside that window, most states allow insurers to do all three.

Some states have expanded protections. The way to think about them is by category: a few states such as New York and Connecticut offer year-round guaranteed issue; Washington allows plan-to-plan switching at any time; a growing group of birthday-rule states, including California and Oregon, give you an annual window around your birthday to switch plans without underwriting, and New Mexico's birthday-rule law takes effect in January 2027. These protections differ in kind, so a flat list would obscure more than it reveals.

Medigap does not include drug coverage. Most Medigap enrollees also need a standalone Part D plan.

In short: Medigap is the most direct way to limit cost-sharing exposure, but the guaranteed-issue window is a one-time opportunity that closes quickly for most people.

Medicare Advantage (Part C) is a different approach. Instead of supplementing Original Medicare, a Medicare Advantage plan replaces it. You still use Medicare; a private insurer approved by CMS (the Centers for Medicare and Medicaid Services) delivers your benefits, often with additional services Original Medicare does not cover.

Most Medicare Advantage plans include prescription drug coverage, making them an all-in-one alternative. Many also offer extra benefits such as dental, vision, and hearing services, though the scope and limits of those benefits are set at the plan level and vary by plan and market.

The structural trade-off is network and prior-authorization requirements. Medicare Advantage plans use defined provider networks, and certain services require prior authorization, which is advance approval before receiving care. Under CMS rule CMS-0057-F, effective 2026, a standard prior-authorization decision must come within 7 calendar days, and an expedited decision when a delay would seriously jeopardize health must come within 72 hours, with any denial required to include a specific reason.

Cost caps and what they mean

One of the clearest advantages of Medicare Advantage over Original Medicare is the mandatory out-of-pocket maximum (MOOP). In 2026, the federal cap on in-network spending is $9,250; the combined in-network and out-of-network cap is $13,900. Plans may set lower limits, and according to KFF, the 2026 enrollment-weighted average in-network MOOP is $5,421. Original Medicare has no equivalent cap.

The trade-off is that reaching the MOOP can still be significant, and network restrictions may affect access to specialists or facilities you prefer. Medicare Advantage is generally a stronger fit for people who are comfortable with a network structure and want predictable benefit packaging in one plan.

In short: Medicare Advantage replaces rather than supplements Original Medicare and adds a cost ceiling, but it introduces network constraints and prior-authorization steps that Original Medicare does not have.

Part D plans cover prescription drugs and are sold as standalone plans for people in Original Medicare or are bundled into most Medicare Advantage plans. They are worth understanding as their own supplemental layer.

In 2026, no Part D plan may set an annual deductible above $615. The bigger change in 2026 is the out-of-pocket cap: under the Inflation Reduction Act, once a beneficiary spends $2,100 on covered Part D drugs in a year, their cost for covered drugs drops to $0 for the rest of the year. The coverage gap (commonly called the donut hole) no longer applies.

If you delay enrolling in Part D after your Initial Enrollment Period (IEP) ends and go 63 or more consecutive days without creditable drug coverage, a late-enrollment penalty applies. The penalty adds 1% of the national base beneficiary premium ($38.99 in 2026) for each full month of the gap, and it is permanent. It attaches to every Part D premium you pay for the rest of your life.

COBRA and retiree coverage do not count as creditable coverage for the purposes of avoiding the Part D penalty in the same way active employer coverage does. If you are leaving a job, verify whether your employer coverage is creditable before assuming your Part D enrollment can wait.

In short: Part D is a necessary supplemental layer for most beneficiaries, and a 63-day gap without creditable coverage triggers a permanent penalty.

Higher earners pay more for both Part B and Part D through a surcharge called IRMAA (the Income-Related Monthly Adjustment Amount). IRMAA uses a two-year lookback, meaning your 2026 premiums are based on your 2024 modified adjusted gross income (MAGI). The structure is a cliff: one dollar over a threshold moves you to the full premium of the next tier.

In 2026, IRMAA begins above $109,000 for single filers and $218,000 for joint filers. The full bracket table renders on the site from the CMS database. At the top tier, which begins at $500,000 single and $750,000 joint, the premium surcharges are substantial. Part D carries a parallel IRMAA surcharge added to whatever plan premium you pay.

If a life-changing event such as retirement, divorce, or the death of a spouse caused your income to drop after the lookback year, you can request a new initial determination using SSA form SSA-44. You can also request reconsideration of an IRMAA determination within 60 days of receiving the notice; SSA treats the notice as received five days after it is dated.

In short: IRMAA is a real cost factor for higher earners and can be contested when income has dropped due to a qualifying life event.

The choice is not about which option is generically better; it comes down to how you use healthcare and what trade-offs you are willing to make.

People who travel frequently, want the ability to see any specialist without referrals, or have complex ongoing conditions often find the predictability of Medigap worth the higher premium. People who prefer a lower upfront cost and are comfortable with a network may find Medicare Advantage a better fit. Neither path forecloses the other permanently; AEP (the Annual Enrollment Period, running October 15 to December 7 each year) allows plan changes, though switching back to Medigap after Medicare Advantage carries underwriting risk in most states.

To find out more about coverage options specific to your situation, please contact us to discuss plan options.

In short: the Medigap versus Medicare Advantage decision hinges on your tolerance for network restrictions, your need for provider flexibility, and how you weigh predictable premiums against lower upfront costs.

The IEP (Initial Enrollment Period) for Medicare is seven months: the three months before your 65th birthday month, your birthday month, and the three months after. Delays in Part B enrollment without qualifying employer coverage trigger a permanent 10% penalty for each full 12-month period of delay. The eight-month Part B SEP (Special Enrollment Period) begins when employment or employer coverage ends, whichever comes first.

For Medigap, the six-month guaranteed-issue window tied to Part B enrollment is distinct from these Medicare enrollment windows. Acting during that window is the most important timing decision most new Medicare beneficiaries face, because protections outside it depend heavily on which state you live in.

The MA OEP (Medicare Advantage Open Enrollment Period) runs January 1 to March 31 each year for people already enrolled in a Medicare Advantage plan who want to switch plans or return to Original Medicare.

In short: timing your enrollment correctly protects your access, your pricing, and your options going forward; the windows do not automatically reopen.