Medicare Supplement Insurance (Medigap) Plans Explained: 2026 Complete Guide
Turning 65 is a major financial milestone — and one of its most critical decisions involves choosing Medicare supplement insurance, commonly called Medigap. With Original Medicare leaving seniors exposed to roughly 20% of medical costs with no out-of-pocket maximum, choosing the right supplement can save tens of thousands of dollars over a lifetime.
What Is Medicare Supplement Insurance?
Medigap policies are sold by private insurance companies and fill the gaps left by Original Medicare (Parts A and B). They cover copayments, coinsurance, and deductibles that Original Medicare doesn't pay.
How Medigap Differs From Medicare Advantage
This is the single most confusing point in Medicare planning. Medicare Advantage (Part C) replaces Original Medicare entirely and is offered by private insurers, while Medigap supplements Original Medicare. You cannot have both simultaneously.
Standardized Medigap Plan Letters
Medigap plans are standardized across the country (with the exception of Massachusetts, Minnesota, and Wisconsin) and identified by letters: A, B, C, D, F, G, K, L, M, and N. Plans F and C are no longer available to newly eligible enrollees as of January 2020.
Best Medigap Plans Compared
The two most popular plans for newly eligible Medicare beneficiaries are Plan G and Plan N.
Medicare Supplement Plan G
Plan G is the most comprehensive plan available to new enrollees. It covers everything Plan F covered except the Part B deductible ($240 in 2026). Premiums typically range from $120 to $250 per month depending on age, location, and carrier.
Medicare Supplement Plan N
Plan N offers slightly lower premiums in exchange for small copays ($20 for doctor visits, $50 for ER visits that don't result in admission). Monthly premiums typically run $90 to $180, making it a strong choice for healthy seniors.
High-Deductible Plan G
For budget-conscious enrollees, High-Deductible Plan G offers extremely low premiums ($30–$60/month) in exchange for a $2,800 annual deductible. It's an excellent fit for healthy seniors who want catastrophic-only coverage.
The same Plan G coverage can cost dramatically different prices depending on the carrier. Major Medigap insurers include:
- Mutual of Omaha
- AARP/UnitedHealthcare
- Aetna
- Cigna
- Humana
- Blue Cross Blue Shield
Differences of $50–$100/month for identical coverage are common, so shopping aggressively is essential.
Medicare Advantage: An Alternative Path
Some seniors choose Medicare Advantage plans instead of Medigap, particularly when budgets are tight.
Medicare Advantage Pros
- Often $0 monthly premium
- Frequently includes prescription drug, dental, vision, and hearing coverage
- Annual out-of-pocket maximums (typically $4,000–$8,500)
- Wellness benefits like gym memberships (SilverSneakers)
Medicare Advantage Cons
- Restricted networks (HMOs require referrals)
- Prior authorization for many services
- Coverage tied to specific geographic regions
- May not travel well — limited coverage outside service area
When Medigap Wins
Medigap is generally superior when:
- You travel frequently or live in multiple states
- You want broad provider choice (any doctor accepting Medicare)
- You have chronic conditions requiring specialist care
- You prefer predictable monthly costs over variable copays
When and How to Enroll
Timing is everything in Medigap. Missing your enrollment window can permanently affect coverage and cost.
The Medigap Open Enrollment Period
You have a 6-month one-time enrollment window starting the month you turn 65 and enroll in Part B. During this period, insurers cannot deny coverage or charge higher rates based on health conditions.
Guaranteed Issue Rights
Outside the open enrollment window, you may still have guaranteed issue rights in specific situations (losing employer coverage, moving out of an Advantage plan service area, etc.). Otherwise, insurers may medically underwrite and deny coverage.
Switching Plans Later
You can switch Medigap plans anytime, but outside open enrollment, insurers can require medical underwriting. Some states (Connecticut, Massachusetts, Maine, New York) have more generous switching rules.
Working with a Medicare Insurance Broker
A licensed Medicare insurance broker can compare dozens of carriers across multiple plan types at no cost to you (brokers are paid by insurance companies). Look for brokers certified by SHIP (State Health Insurance Assistance Program) or with independent fiduciary status.
Final takeaway: Medigap is one of the most consequential financial decisions seniors make. Take advantage of your one-time open enrollment, compare quotes across at least 5 carriers, and lean toward Plan G for comprehensive lifetime protection.