Medicare Advantage vs Medigap: Which Is Right for You?

When you first sign up for Medicare, one decision shapes your costs and your choices for years: do you stay with Original Medicare and add a Medigap (Medicare Supplement) policy, or do you enroll in a Medicare Advantage plan? Both are legitimate ways to cover the gaps in Parts A and B, but they work in opposite directions. Medicare Advantage bundles everything into one private plan with networks and copays; Medigap layers predictable, nationwide coverage on top of the government program you already have. There is no single "best" answer, because the right choice depends on your health, your budget, your doctors, and how much financial surprise you can tolerate.

Here is the part almost no one explains clearly at 65: this is not a decision you can freely reverse. You get one federally guaranteed, six-month window to buy any Medigap policy without answering a single health question. Miss it, and in most states an insurer can look at your medical history, charge you more, or turn you down entirely. Medicare Advantage, by contrast, welcomes you back every year. That asymmetry — easy to leave Medigap for later, hard to return — is the real hinge of this decision, and it is why "I'll just switch if I don't like it" is dangerous advice. This guide gives you a decision framework built around that hinge, not a ranking of plans.

What each option actually is

Original Medicare plus Medigap. You keep Original Medicare (hospital Part A and medical Part B), which lets you see any doctor or hospital in the country that accepts Medicare — no networks, no referrals. Original Medicare alone leaves you exposed to deductibles, the 20% coinsurance on Part B services, and, critically, no annual cap on what you can spend. A Medigap policy is private insurance that fills those gaps. Plans are standardized and sold by letter (A, B, D, G, K, L, M, N, and high-deductible F and G), so a Plan G from one insurer covers exactly the same things as a Plan G from another — they compete on price and service, not benefits. Plan G is the most popular choice for people who became eligible on or after January 1, 2020; it covers nearly everything Original Medicare doesn't, except the annual Part B deductible ($283 in 2026).

Medicare Advantage (Part C). This is an all-in-one alternative offered by private insurers that Medicare pays to take over your coverage. The plan replaces the way your Original Medicare benefits are delivered — you still owe your Part B premium — and usually folds in Part D drug coverage plus extras Original Medicare never offered, like dental, vision, hearing, and gym memberships. Many plans advertise a $0 monthly premium in 2026. The trade-offs: you generally must use the plan's network (HMO or PPO), you may need referrals and prior authorization, and you pay copays and coinsurance as you go until you hit the plan's out-of-pocket maximum.

The hinge: your one-time 6-month Medigap Open Enrollment

Your Medigap Open Enrollment Period starts the first month you are both 65 or older and enrolled in Part B, and it lasts exactly six months. During this window you have a "guaranteed issue" right: any insurer must sell you any Medigap policy it offers, at its best available price, and cannot deny you or charge more because of pre-existing conditions. This is the one time federal law hands you that power for good.

Once those six months pass, the rules flip in most states. Outside a short list of special guaranteed-issue situations, insurers can use medical underwriting: they can review your health history and legally deny your application, charge a higher premium, or impose a waiting period for pre-existing conditions. So a common path — "I'll take a cheap or $0 Medicare Advantage plan now and move to Medigap later if my health changes" — can quietly close the Medigap door precisely when you most need it. The moment you develop the conditions that make comprehensive coverage valuable is often the moment underwriting makes Medigap expensive or unavailable.

Two enrollment calendars govern later changes, and neither restores your Medigap guaranteed-issue right. The Medicare Annual Enrollment Period (October 15–December 7) lets you join, switch, or drop a Medicare Advantage or Part D plan for the following year. The Medicare Advantage Open Enrollment Period (January 1–March 31) lets people already in an Advantage plan switch to another one or return to Original Medicare. You can always get back into Medicare Advantage; getting back into Medigap is the part that may require passing a health exam.

A side-by-side decision framework

Use the table below to weigh the factors that actually differ. Read it as a set of trade-offs, not a scorecard — the column that fits you depends on which rows matter most for your life.

Cost is more than the monthly premium

A $0-premium Medicare Advantage plan is not free care; it front-loads savings and back-loads risk. You pay copays and coinsurance each time you use services, up to the plan's annual out-of-pocket maximum. In a healthy year you may spend almost nothing. In a year with surgery, chemotherapy, or a long hospital stay, you could pay thousands before hitting the cap — and if a needed provider is out of network, those costs can climb further. Medigap flips the math: you pay a steady monthly premium in exchange for very small bills at the point of care, which is exactly what people with chronic or expensive conditions tend to value.

Everyone pays the standard Part B premium ($202.90/month in 2026) regardless of path, and Original Medicare's Part B deductible is $283 in 2026. Drug costs also matter to the comparison. Under Part D in 2026, the standard deductible is up to $615, and — new and significant — once your out-of-pocket spending on covered drugs reaches $2,100, you pay nothing more for the rest of the year (note: the cap is $2,100 in 2026, not $2,000). The Medicare Prescription Payment Plan can spread that out-of-pocket amount across the year in monthly installments instead of one painful hit at the pharmacy. If you choose Medigap, you buy a stand-alone Part D plan to get this protection; if you choose most Medicare Advantage plans, Part D is already built in. High-deductible Medigap options (high-deductible Plan G and Plan F) carry their own annual deductible — $2,950 in 2026 — before full coverage kicks in.

All of these figures are indexed and change every year — amounts are indexed annually, so confirm the current-year numbers on Medicare.gov before you decide.

An if/then checklist to narrow your choice

• If you travel often, split time between states, or want to keep a specific doctor or top hospital, then Original Medicare + Medigap's network-free access is a strong reason to lock it in during your 6-month window.
• If your budget can't absorb a higher monthly premium right now and you're generally healthy, then a low- or $0-premium Medicare Advantage plan may fit — but go in knowing the return trip to Medigap isn't guaranteed.
• If you have a chronic condition, a family history that worries you, or simply want the most predictable bills, then lean toward Medigap while you can still get it without underwriting.
• If you value bundled dental, vision, and hearing and are comfortable with networks and prior authorization, then Medicare Advantage's extras may be worth the trade-offs.
• If you're unsure, then the conservative move is to secure Medigap during your one-time window; you can always switch to Medicare Advantage later, but the reverse may not be available.

How this varies by state and year

Federal rules set the floor, but states can be more generous — and a few are dramatically so. New York and Connecticut require insurers to sell Medigap policies year-round on a guaranteed-issue basis, so residents there can switch without underwriting at any time. Roughly a dozen and a half states have a "birthday rule" that gives current Medigap policyholders a limited annual window around their birthday to switch to a comparable or lesser plan with a different insurer without answering health questions. As of 2026, birthday-rule states include California, Oregon, Illinois, Idaho, Nevada, Louisiana, Maryland, and several others, but the exact window length and switching limits differ by state (some allow 30 days, most 60, a few 63). Your state department of insurance is the authority on what applies to you.

Timing matters too. Medicare Advantage plans change their networks, formularies, copays, and extra benefits every year, so a plan that fit you in one year may not the next — reviewing your coverage each fall during the Annual Enrollment Period (October 15–December 7) is essential. Medigap benefits are standardized and don't shift year to year, but premiums rise over time and pricing methods vary. And because Medigap availability outside your open enrollment window depends on state law and insurer underwriting, always verify the current rules with your state department of insurance and Medicare.gov before assuming you can switch.

Who should NOT default to one side

Some people should slow down before assuming Medigap is the safe pick. If you truly cannot afford a Medigap premium on top of Part B, forcing it isn't "safe" — an unaffordable policy you drop provides no protection. If you qualify for both Medicare and Medicaid, or for a Medicare Savings Program, your situation is different: certain Medicare Advantage Special Needs Plans or other supports may serve you better, and Medigap may be unnecessary or not the priority. And if you're still covered by employer or union insurance, or have retiree or VA/TRICARE coverage, adding Medigap or jumping into Medicare Advantage may duplicate what you already have — check how your existing coverage coordinates with Medicare first.

Equally, Medicare Advantage is the wrong default for some. If you rely on a specific cancer center or specialist that isn't in a plan's network, if you travel or live in more than one state, or if an unpredictable copay in a bad-health year would genuinely threaten your finances, the network limits and pay-as-you-go structure can cost you far more than a steady Medigap premium. The honest answer for most people is that the choice turns on your health, your providers, your budget, and your appetite for financial surprise — and on the calendar. Whatever you decide, decide with your six-month Medigap window in mind, because it is the one part of this that doesn't come back around.

This process moves fast at 65. If you take one thing from this guide, let it be this: before you pick a low-cost plan now, make sure you understand what it costs to change your mind later. Use Medicare's Plan Finder to compare specifics, and talk to your free State Health Insurance Assistance Program (SHIP) for unbiased, no-commission help with your exact situation.

This article is for general educational purposes only and is not insurance, legal, tax, or medical advice. Medicare rules, plan availability, and dollar amounts change and vary by state and insurer. Verify all details with Medicare.gov, your State Health Insurance Assistance Program (SHIP), or your state department of insurance before making enrollment decisions.