Medigap: The Supplement That Fills the 20% Hole
Original Medicare pays 80% of covered Part B services and stops. Medigap — Medicare Supplement Insurance — exists to cover the remaining 20% and the deductibles, converting an open-ended liability into a fixed monthly premium. If you choose Original Medicare, this is the decision that determines whether a bad year is survivable.
How it works
Medigap plans are sold by private insurers but standardized by letter. A Plan G from one insurer covers exactly the same things as a Plan G from another — only price, service and rate stability differ. That makes it one of the rare insurance products you can genuinely shop on price alone, once you have picked a letter.
| Plan | Broad shape |
|---|---|
| Plan G | The most comprehensive available to people newly eligible; covers essentially everything except the Part B deductible |
| Plan N | Lower premium, small copays for some visits, does not cover excess charges |
| High-deductible G | Much lower premium, you pay a set deductible first — catastrophic-style coverage |
| Plan F | Historically the most complete; closed to people who became eligible after a cutoff, still held by many existing enrollees |
The six-month guaranteed issue window is the whole ballgame. Starting the month you are 65 and enrolled in Part B, you have six months during which any Medigap insurer in your state must sell you any policy they offer, at their standard rate, regardless of your health. After that window closes, in most states they may underwrite — ask health questions, charge more, or decline you outright. A few states have more generous rules. Everywhere else, this is a one-time door.
What it does not cover
Medigap covers gaps in Original Medicare. It does not provide drug coverage — you need a separate Part D plan — and it does not cover dental, vision, hearing or long-term care. It also cannot be combined with a Medicare Advantage plan; you have one or the other.
Shopping it
- Pick the letter first, based on how much predictability you want.
- Then compare premiums across insurers for that identical letter — spreads between carriers for the same coverage are frequently large.
- Ask how the insurer rates premiums: by attained age, issue age or community. Attained-age policies start cheap and rise as you get older, which is exactly when you can least afford it.
- Ask about the carrier's history of rate increases, not just today's price.
- Check whether your state has an annual switching right — some do.
Frequently Asked Questions
Is Medigap worth the premium?
It is the mechanism that gives Original Medicare an effective ceiling. If you have chosen Original Medicare and cannot absorb an unlimited 20%, then yes.
Can I be turned down?
Outside guaranteed-issue periods, in most states, yes.
Do I still need Part D?
Yes. Medigap does not include drug coverage, and going without creditable drug coverage accrues a permanent penalty.
Can I switch Medigap plans later?
You can apply, but you may be underwritten. Some states guarantee an annual window; most do not.
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