A medigap policy, formally Medicare Supplement Insurance, is private coverage designed to sit alongside original Medicare and pick up the costs Medicare leaves on your plate: deductibles, copays, and coinsurance. It exists because original Medicare, on its own, covers roughly 80 percent of many costs and leaves the rest to you indefinitely, with no annual out-of-pocket cap. This is general information, not personalized financial or medical advice; verify current plan letters, pricing, and rules directly with Medicare.gov or a licensed insurance agent.
What changed in 2026
- Plan availability continues to shift — some older plan letters are closed to new enrollees who became Medicare-eligible after a certain date, so confirm which letters are actually available to you.
- Pricing methods (community-rated, issue-age-rated, attained-age-rated) remain a major driver of long-term cost differences between otherwise identical standardized plans — this is worth understanding before you buy, not after.
- State-specific rules on guaranteed issue outside the initial enrollment window continue to vary, making the timing of your purchase even more consequential depending on where you live.
How standardization works
Medigap plans are identified by letters — Plan G and Plan N are common examples — and federal rules standardize what each lettered plan must cover. This means a Plan G from one insurer covers exactly the same benefits as a Plan G from a different insurer; the only real differences between insurers offering the same letter are price, customer service, and financial stability. This standardization is meant to make comparison shopping straightforward once you know which letter you want.
Why the purchase window matters so much
Your Medigap open enrollment period, generally the six months starting when you are 65 and enrolled in Part B, is the one guaranteed window to buy any available plan without medical underwriting, regardless of health conditions. Miss that window in most states, and insurers can use your health history to charge more or deny coverage outright. This single timing decision often matters more than which specific letter plan you eventually choose.
Comparing your Medicare paths
| Path |
Covers Medicare gaps |
Extra premium |
Network restrictions |
| Original Medicare alone |
No |
None |
None, but no cap on cost-sharing |
| Original Medicare + Medigap |
Yes |
Yes, monthly Medigap premium |
Generally none, wide provider access |
| Medicare Advantage |
Built-in differently |
Often lower or $0 added premium |
Usually yes, network-based |
Medigap versus Medicare Advantage
These two paths are alternatives, not complements — you generally cannot have both. Medigap pairs with original Medicare and offers broad provider access with predictable added cost-sharing coverage, usually at a higher monthly premium. Medicare Advantage often has a lower or no added premium but uses provider networks and different cost-sharing structures. The choice interacts with other coverage decisions too, including drug coverage — see Medicare Part D explained, since Medigap plans generally do not include drug coverage and require a separate Part D plan.
What Medigap does not cover
Medigap does not cover prescription drugs (that is Part D's role), long-term custodial care (see what is long-term care insurance), or care outside the United States beyond limited emergency provisions in some plans. It is specifically a cost-sharing supplement to original Medicare, not a replacement for other coverage types.
FAQ
Can I switch Medigap plans later?
Yes, but outside your initial open enrollment window, insurers in most states can require medical underwriting, potentially raising your price or denying coverage.
Does Medigap work with Medicare Advantage?
No, they are not meant to be combined — Medigap is designed to supplement original Medicare specifically.
Why do identical Plan G policies cost different amounts?
Because the benefits are standardized but the pricing is not — insurers set their own premiums and use different pricing methods that affect how costs rise over time.
Do I need Medigap if I am healthy and rarely see doctors?
It depends on your risk tolerance — original Medicare has no annual cap on cost-sharing, so a serious unexpected illness without Medigap could mean substantial out-of-pocket costs.
Where to go next
Related reading: Medicare Part D explained, Medicare vs Medicaid explained, and what is long-term care insurance.