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If you turned 65 last spring, you already know the drill. The mailbox fills with envelopes promising lower premiums, free dental, a gym membership you’ll never use. Even after you sort them by postage you’ve still got a stack. The detail that actually matters isn’t in any of them. It’s a single capital letter, A through N, printed near the top of a Medigap policy.
Medigap is the private insurance that picks up where Original Medicare stops paying. Part A covers your hospital stay but leaves you a deductible that runs $1,676 in 2025. Part B pays 80% of most outpatient care and leaves you the other 20%, permanently, with no annual ceiling. A rough cancer treatment or a couple of surgeries and that 20% can run into five figures. Medigap exists to make that number disappear.
What a Medigap Policy Actually Does
You keep your Original Medicare card. You see any doctor or hospital in the country that accepts Medicare. No networks, no referrals, no prior authorization before a specialist visit. The Medigap carrier simply receives the bill after Medicare pays its share and covers most or all of the remainder.
Three limits are worth knowing up front. Medigap does not include prescription drug coverage, which comes from a separate Part D plan. It cannot be paired with Medicare Advantage, since the two are mutually exclusive. And in most states insurers can refuse to sell it to you if you’re under 65 and on disability.
If you want the mechanical version of how claims move between Medicare and the supplement carrier, this explanation of how Medigap fills the gaps in your coverage walks through it clearly.
Ten Letters, One Set of Rules
Federal law requires every insurer to sell identical benefits under the same letter. A Plan G from one company covers exactly what a Plan G from another covers, down to the dollar. Price, rate stability, and service are the only real variables.
- Plan A – the base model. Part A coinsurance, 365 extra hospital days, hospice, first three pints of blood. Cheap and thin.
- Plan B – Plan A plus the Part A hospital deductible.
- Plan D – adds skilled nursing facility coinsurance, foreign travel emergency care, and Part B excess charges.
- Plan G – the near-complete package, missing only the Part B deductible.
- Plan K – pays 50% of most benefits with an out-of-pocket cap near $7,220.
- Plan L – pays 75% with a cap near $3,610.
- Plan M – covers half the Part A deductible plus most other gaps, but not excess charges.
- Plan N – Plan G with small office and ER copays and no excess charge coverage.
- Plans C and F – the old top-tier pair, closed to anyone newly eligible after January 1, 2020.
Why Plan F Disappeared
Plans F and C were the bestsellers for decades. Congress cut them off for new enrollees because plans that absorb the Part B deductible tend to encourage more doctor visits, which costs the program money. If you already owned one, you can keep it and keep renewing it. If you’re turning 65 now, it isn’t an option.
Plan G Became the Default
Plan G is the most popular letter on the shelf. It covers everything Plan F did except the $257 Part B deductible, and premiums typically run 20% to 30% lower. A high-deductible version of G exists too, with a deductible around $2,870 in 2025 and premiums that can drop below $60 a month for a healthy 65-year-old in competitive markets.
Plan N Is the Budget Compromise
Plan N looks like G with two catches. You pay up to $20 for some office visits and up to $50 for an emergency room trip that doesn’t lead to an admission, and it doesn’t cover Part B excess charges. Those charges only bite when a provider bills above the Medicare-approved rate, which is uncommon but real. For someone who sticks with assigned providers, Plan N saves $40 to $70 a month over G.
What No Medigap Plan Will Pay For
Every letter shares the same exclusions:
- Prescription drugs, which fall under Part D
- Dental work, vision exams, and hearing aids
- Long-term custodial care in a nursing home
- Private-duty nursing
- Care received outside the United States, apart from a limited foreign travel emergency benefit on a few letters
That’s why some people stack a standalone dental policy or a hearing aid discount plan on top. Budget for those separately rather than expecting a supplement to stretch.
The Six-Month Window That Sets Your Price
You get a one-time open enrollment period that begins the month you’re 65 and enrolled in Part B, and it runs six months. During that window, no insurer can turn you down, charge you more because of a health condition, or impose a waiting period before coverage starts.
This is the most valuable protection in Medicare. Use it. If you have diabetes, a cancer history, or a stent, those six months are your one reliable chance to buy Medigap at a standard rate.
Once the Window Shuts, Underwriting Begins
Outside open enrollment, most states let insurers ask health questions. Answer in a way they don’t like and you get declined or rated up. There are exceptions:
- Federal guaranteed-issue rights apply in specific situations, including losing employer coverage, moving out of a plan’s service area, or a Medicare Advantage plan exiting your county.
- Connecticut, Massachusetts, Maine, and New York offer year-round or near-year-round guaranteed issue.
- California, Oregon, Idaho, Illinois, Nevada, Missouri, and Washington give residents a birthday window each year to switch without answering health questions.
Live in one of those states and you can chase a lower premium later. Live anywhere else and treat your first Medigap choice as close to permanent.
Three Ways Insurers Price the Same Plan
Community-rated premiums stay the same whether you’re 65 or 85, though they rise with inflation across the whole pool. Issue-age-rated premiums lock in at whatever age you were when you enrolled. Attained-age-rated premiums climb every single year, which makes them cheap today and expensive at 80. Ask which method a carrier uses before comparing quotes, because a $98 attained-age premium and a $140 community-rated premium are not the same product over 20 years.
Ask about household discounts as well. Plenty of carriers knock 5% to 12% off when two people in a home enroll, and another few percent for automatic bank draft.
Medigap or Medicare Advantage? The Fork in the Road
These are two different philosophies. Medigap means higher fixed premiums, near-zero surprises at the point of care, and total provider freedom. Medicare Advantage means low or zero premiums with copays, networks, and an out-of-pocket cap that reaches $9,350 for in-network care in 2025.
Travel a lot, have a specialist you refuse to leave, or want predictable costs? Medigap wins. Healthy, cost-focused, comfortable staying in a local network? Advantage can be a fair trade. Picking between the two is a different exercise than picking a letter, and choosing a Medicare Advantage plan without the headache covers that side of the decision.
Carrier reputation matters less with Medigap than with Advantage, since benefits are fixed by law, but claims handling still varies. It’s worth reading up on how UnitedHealthcare’s Medicare plans actually work and what Humana’s Medicare plans, costs, and enrollment look like before assuming the biggest logos deliver the smoothest service.
How to Shop Without Getting Played
Start with your state insurance department website, which publishes rate filings and complaint ratios. Then work through the list:
- Get quotes for the same letter from at least five carriers in your ZIP code.
- Ask each one for the last three years of rate increases, not just the current premium.
- Confirm whether the rate is attained-age, issue-age, or community-rated.
- Check financial strength (A.M. Best A or better) and the complaint index.
- Verify the agent represents multiple carriers. A captive agent can only show you one.
Commissions on standardized plans are similar across letters, so a recommendation of G over N usually reflects your situation rather than a fatter check. Ask anyway: “Which carriers do you represent?” A good answer is a list. A bad answer is a single logo.
Don’t sign anything in the first week of your window. Premiums for identical coverage in the same ZIP code routinely differ by 60% or more between carriers, so collecting five quotes isn’t overkill. It’s the minimum.
