If you have Original Medicare, you already know it does a lot of the heavy lifting. It doesn't cover everything, and it doesn't have a cap on what you could owe out of pocket in a given year. That gap is exactly what Medicare Supplement insurance, often called Medigap, was designed to fill. It's a private insurance policy that works alongside Original Medicare, picking up some or all of the costs Medicare leaves on the table: things like coinsurance, copayments, and deductibles.
The idea is simple even if the decision isn't always easy: you pay a monthly premium for the Medigap policy, and in exchange, you get much more predictable costs when you actually need care. Instead of wondering how much a hospital stay or a series of specialist visits will cost, a lot of that uncertainty gets smoothed out. That predictability is a big part of why Medigap appeals to people who want fewer surprises in their budget, even if it means a higher fixed cost every month.
Not all Medigap plans are the same, and this is where Plan G and Plan N tend to come up in almost every conversation about supplement coverage. Plan G is the most comprehensive option generally available to people newly eligible for Medicare, covering nearly all the gaps left by Original Medicare except the Part B deductible. Because it covers so much, it tends to carry a higher premium, but for many people, the trade-off is worth it in exchange for rarely thinking about a medical bill again.
Plan N takes a slightly different approach. It usually comes with a lower monthly premium than Plan G, but it asks you to share a little more of the cost when you use care, typically a small copayment for office visits and emergency room visits that don't result in an admission, plus the Part B excess charges that Plan G would otherwise cover. For someone who doesn't expect to need frequent care and would rather save on the premium, Plan N can strike a comfortable middle ground between cost and coverage.
Choosing between the two often comes down to a personal read on risk and budget: how much would you rather pay predictably every month, versus how much would you be comfortable paying occasionally when you actually see a doctor? There's no universally correct answer. It depends on health history, how often someone expects to need care, and what feels manageable on a monthly budget.
Timing, though, is where things get genuinely important, and it's the part of Medigap that surprises people most. When you first enroll in Medicare Part B, you get a six-month Medigap Open Enrollment Period. During that window, insurance companies have to sell you any Medigap policy they offer, at their standard rate, regardless of your health history. That's called guaranteed issue, and it's a powerful protection: no medical underwriting, no denial for a pre-existing condition, no higher premium because of your health.
Miss that window, though, and the picture changes. Outside of a handful of specific protected situations, insurance companies can generally ask health questions and may charge more, add a waiting period, or decline coverage altogether based on your health history. That's why so much of the practical advice around Medigap centers on timing: understanding exactly when your open enrollment period starts, and making a decision before it closes, rather than waiting and hoping a plan will still be available on the same easy terms later.
None of this is meant to rush a decision. It's simply worth knowing the clock is real, so that whatever choice you make about Plan G, Plan N, or another option entirely, it's made with the timing in mind rather than discovered after the fact.