Medigap (Medicare Supplement Insurance) is private insurance that helps pay some costs that Original Medicare (Part A hospital and Part B medical) leaves to you: deductibles, coinsurance, and copayments. It is not the same product as Medicare Advantage (Part C), and it is not long-term care insurance.
If you are still on employer coverage, map exit timing with COBRA health coverage before you assume Medicare day one. Deductible vocabulary still applies: Health insurance deductibles.
What Medigap is (and is not)
| Product | Role |
|---|---|
| Original Medicare (A + B) | Federal program that pays a share of covered hospital and medical services |
| Medigap (Supplement) | Private policy that helps with Original Medicare cost-sharing; standardized letter plans in most states |
| Medicare Advantage (Part C) | Private plan that replaces Original Medicare for covered services; usually has its own network and OOP max |
| Part D | Prescription drug coverage (often separate if you keep Original Medicare + Medigap) |
| Long-term care insurance | Helps with custodial nursing/home care Medicare generally does not cover (Long-term care insurance) |
Medigap policies sold to people new to Medicare are standardized by letter (Plan G, Plan N, and others; Plan F is generally closed to newly eligible people). Benefits for a given letter are the same across insurers in most states; premiums and customer service differ. Massachusetts, Minnesota, and Wisconsin use different standardization systems.
Gaps Original Medicare leaves
Original Medicare typically involves Part A and Part B deductibles, Part B 20% coinsurance on many services with no annual out-of-pocket maximum like many employer PPOs. That open-ended coinsurance is a major reason people buy Medigap. Premium vs deductible tradeoffs in general insurance language: Premiums vs deductibles.
Medigap does not usually cover dental, vision, hearing aids, or long-term custodial care. Foreign travel emergency benefits appear only on some letters, with limits.
Worked example: outpatient surgery coinsurance
Sam has Original Medicare. An outpatient procedure’s Medicare-approved amount is $10,000. After Sam meets the Part B deductible for the year, Medicare Part B pays 80% ($8,000). Sam’s 20% coinsurance is $2,000 before any supplement.
- Without Medigap: Sam owes about $2,000 (plus any noncovered items).
- With a Medigap Plan G (illustrative): Plan G typically covers Part B coinsurance after the Part B deductible; Sam’s out-of-pocket for that coinsurance slice can drop sharply, while Sam still pays the Part B deductible and the Medigap premium.
- With Medicare Advantage: Sam would follow that plan’s copays and network rules instead; Medigap generally cannot be paired with Advantage.
Exact dollar splits depend on the year’s official deductibles and the plan letter. Always read the outline of coverage from the insurer (UnitedHealthcare, Humana, Mutual of Omaha, and many Blues sell Medigap in various states).
When people buy Medigap
- They want freedom to see any provider that accepts Medicare (no Advantage network gate)
- They prefer predictable cost-sharing after a monthly premium
- They are in a Medigap open enrollment window (typically the first six months of Part B at 65+) when federal rules give strong guaranteed-issue protections in most situations
Outside protected windows, insurers in many states may underwrite (health questions) unless a guaranteed-issue right applies. Rules are state-specific; use Medicare.gov and your state insurance department.
Medigap vs “just pay cash for gaps”
Paying coinsurance from savings can work for small years and fail in a high-claim year because Original Medicare has no in-network-style annual OOP cap. Hospital charity care and bill negotiation still matter for noncovered or disputed charges (Medical bills and insurance; Out-of-network medical bills when providers sit outside what you expected).
Checklist
- Confirm you are on (or enrolling in) Original Medicare, not Advantage, before shopping Medigap.
- List letter plans available in your state; compare premiums for the same letter.
- Check household doctors/hospitals accept Medicare assignment.
- Add Part D (drug) coverage if you keep Original Medicare + Medigap.
- Calendar Medigap open enrollment and any state trial or birthday rules.
- Do not confuse Medigap with long-term care or hospital indemnity riders.
Medicare Advantage MOOP vs Original Medicare + Medigap cost-sharing: Medicare Advantage MOOP basics.
Medigap generally does not fill Part D the way it fills A/B—coverage-gap basics: Medicare Part D donut hole basics.
IRMAA can raise Part B/D premiums even when you keep Original Medicare + Medigap: Medicare IRMAA basics.
Part B late-enrollment penalties stay on the Medicare premium even if you buy Medigap: Medicare late enrollment penalty basics.
Part B excess charges from non-participating providers—and which Medigap letters help: Part B excess charge basics.
Medigap six-month open enrollment and later underwriting: Medigap open enrollment basics.
How the annual Part B deductible works and which letters help: Medicare Part B deductible basics.
Medigap guaranteed-issue rights when you are outside open enrollment: Medigap guaranteed issue basics.
How Part A hospital benefit periods and deductibles reset: Medicare Part A benefit period basics.
Observation vs inpatient status still matters with Medigap: Observation status vs inpatient basics.
How Medigap letters may help with SNF coinsurance inside a benefit period: Skilled nursing benefit period basics.
How letters may help with hospital coinsurance after day 90: Medicare lifetime reserve days basics. Home health episodes under Original Medicare vs Advantage cost-sharing: Home health episode of care basics.
Hospice election periods and limited hospice cost-sharing alongside Medigap: Hospice election period basics.
How Medigap letters often cover SNF coinsurance on days 21–100: Medicare skilled nursing copay basics.
Medicare Advantage star ratings (Advantage/Part D tool—not a Medigap letter grade): Medicare Advantage star ratings basics.
Hospice inpatient respite coinsurance cues alongside Medigap: Medicare respite care basics.
How Part B outpatient therapy thresholds and KX interact with coinsurance Medigap may cover: Medicare outpatient therapy threshold basics.
High-deductible Plan G premium vs deductible tradeoff: High-deductible Medigap Plan G basics.
Plan N office-visit and ER copays vs Plan G: Medigap Plan N copay basics.
Educational only. Not insurance, tax, or legal advice. Medicare and Medigap rules are federal and state-specific and change; confirm with Medicare.gov, your state SHIP program, and insurer outlines of coverage.