Medigap plans — supplemental insurance that fills the holes

This article is for educational purposes only and does not constitute medical, legal, or financial advice. Every family situation is different, and you should consult with appropriate professionals about your specific circumstances.

When you start learning about Medicare, everyone talks about Original Medicare, and then everyone mentions Medigap in the same breath as if you should already know what it is. The reality is that Medigap might be the most important insurance decision your parent makes, and it's one of the least explained by people who aren't getting paid to explain it.

Here's the actual situation: Original Medicare, while comprehensive in many ways, leaves holes. Big ones. Your parent could face thousands of dollars in costs that Medicare won't pay. These aren't rare edge cases. These are normal, everyday costs that pile up. Medigap exists specifically to fill those holes, and understanding how it works will probably save your parent more money than anything else you do to help with their healthcare costs.

But it's not magic. It's not one-size-fits-all. And the window to get it right is surprisingly narrow.

Why Medigap Exists: The Gaps in Original Medicare

Let's start with what Medicare actually covers. Original Medicare Part A covers hospitalization and skilled nursing care. Part B covers doctor visits and outpatient care. The trouble is that Medicare doesn't cover the full cost of these things. It covers part of it, and your parent pays the rest.

This isn't mysterious or hidden. It's just how the system was designed. Medicare pays a certain percentage. Your parent pays the rest in the form of deductibles, copays, and coinsurance. On a routine doctor visit, this might be $20 or $50. But if your parent needs serious treatment—cancer care, heart disease management, a long hospitalization—these costs add up fast and hit no ceiling. There's no out-of-pocket maximum with Original Medicare Part B. The costs just keep coming.

Real example: your parent gets admitted to the hospital for a serious infection. They stay for five nights. Under Original Medicare Part A, your parent pays a $1,632 deductible for the hospital stay, plus copays for each night after the first three nights. That's before they even leave the hospital. Then they go to a skilled nursing facility for rehabilitation, and they start paying copays there too. A two-week facility stay could easily cost them $2,000 to $3,000 in copays alone.

Then they see their cardiologist, and each visit has a copay. Each lab test has a cost. Each medication might have a copay, depending on their drug plan. Over months of recovery, they could spend $5,000 or $10,000 out of their own pocket.

Medigap is supplemental insurance sold by private insurance companies. It specifically fills these gaps—the copays, the coinsurance, the deductibles that Medicare leaves for your parent to pay. It's not a Medicare replacement. It's not an alternative to Original Medicare. It exists alongside Original Medicare to fill in the parts Medicare doesn't cover.

Think of it this way: Medicare is the foundation. Medigap is the protection that goes on top, catching what the foundation doesn't cover.

How Medigap Works: The Relationship to Original Medicare

This is important because it's different from how Medicare Advantage works, and the difference creates clarity or confusion depending on how you think about it.

When your parent has Original Medicare plus a Medigap plan, here's what happens: they go to their doctor. The doctor bills Medicare. Medicare pays its share. Then the doctor submits the remaining bill to your parent's Medigap insurance company. The Medigap company pays what's covered under the plan your parent bought. Your parent pays whatever's left, which is usually small or nothing.

So your parent has two insurance companies now. Original Medicare is one. The Medigap insurance company is another. They work together. Your parent goes to any doctor who accepts Medicare because Original Medicare has no network. The Medigap plan supplements Original Medicare across any provider your parent chooses.

This is what makes Original Medicare with Medigap so powerful for people with complex medical needs. Your parent has complete freedom to see any provider they want. The Medigap plan protects them from financial disaster. There's an out-of-pocket maximum, sort of. Once your parent hits a certain amount of costs in a calendar year, the Medigap plan covers everything else. Different Medigap plans have different maximums, but they're all designed to protect your parent from catastrophic costs.

Your parent still needs to choose a Part D prescription drug plan separately. Medigap doesn't cover prescriptions. But everything else,hospital costs, doctor costs, lab costs,Medigap covers the gaps.

The Lettered Plans: Understanding What You're Buying

Medicare offers standardized Medigap plans labeled with letters. A, B, C, D, F, G, K, L, M, N. There used to be more, but the standardized plans are what are available now. Each letter represents a different combination of coverage.

The key thing to understand is that the letter doesn't matter. Plan A from Aetna is exactly the same as Plan A from Humana. The same benefits, the same coverage, the same restrictions. What differs is the monthly premium. One insurance company might charge $150 a month for Plan A while another charges $175. That's the only real difference.

The differences between letters are what matter. Plan A covers certain gaps. Plan G covers different gaps. Plan N covers yet other combinations.

Plan G is probably the most popular choice for people around age 65 to 75 with average healthcare costs. Plan G covers most gaps in Original Medicare. It covers the hospital deductible. It covers copays and coinsurance. The one thing Plan G doesn't cover is the Part B deductible, which is $240 a year. So your parent pays that one deductible, then Medigap covers the rest.

Plan A is cheaper than Plan G but covers less. Plan A also doesn't cover the Part B deductible, plus it has some copays for doctor visits and emergency room visits that Plan G doesn't have. Plan A works okay for people who don't expect heavy medical usage.

Plan N is a middle ground. It's cheaper than Plan G but covers more than Plan A. Plan N has some copays your parent might pay, but not as many as Plan A. If your parent is price-conscious but wants reasonable protection, Plan N might fit.

There are other plans with different benefit structures, like Plan K or Plan L, which have different cost-sharing arrangements, or plans with annual out-of-pocket maximums. But most people end up with Plan A, Plan G, or Plan N because they represent the main trade-offs between cost and coverage.

The honest truth is that Plan G is the most comprehensive for most situations. But "most comprehensive" costs more per month. Your parent has to decide whether the peace of mind is worth the extra $30 or $50 per month.

When to Buy Medigap: Open Enrollment Advantages

This is where timing becomes important. Your parent can apply for a Medigap plan at any time, but there's a special period where insurance companies must sell them Medigap without asking health questions or excluding pre-existing conditions.

This special period is called the Open Enrollment Period for Medigap, and it's the first 63 days after your parent enrolls in Medicare Part B. This is typically around their 65th birthday plus 63 days.

During these 63 days, your parent can apply for any Medigap plan and any insurance company must accept them. No health questions. No exclusions. Your parent can't be turned down.

After the 63-day window closes, things change. Insurance companies can ask health questions. They can exclude conditions your parent already has. They can turn your parent down entirely. And if they do accept your parent, they can charge more based on your parent's age and health history.

In some states, the price of Medigap is the same regardless of age or health (called community rating). In other states, your parent's age affects the price (age rating or attained age rating). If your parent applies during the Open Enrollment Period at age 65, they lock in rates based on age 65. If they wait until age 70 to apply, they'll pay higher rates based on age 70, and those rates might never come down.

This is why waiting to buy Medigap is expensive. Your parent might save money in the short term by not paying premiums before they actually need Medigap. But when they do apply later, they'll pay higher premiums for the rest of their life, which easily wipes out whatever they saved.

The other situation is if your parent initially chose Medicare Advantage and then decides to switch to Original Medicare with Medigap. If they switch during the Annual Enrollment Period, they lose their guaranteed Open Enrollment rights. They can still apply for Medigap, but insurance companies can now ask health questions and charge more. Your parent might not even get approved for their preferred plan.

So the timing of the Medigap decision matters. The Open Enrollment Period after Part B enrollment is the golden window. Miss it, and your parent is making a more expensive choice from then on.

The Trade-offs: Medigap vs. Medicare Advantage

This deserves its own article, and we have one. But quickly: Original Medicare plus Medigap costs more per month in premiums than Medicare Advantage. Your parent might pay $200 to $300 a month for Part B and Medigap together, depending on the Medigap plan they choose and where they live. Medicare Advantage might be free or $50 a month.

But the out-of-pocket costs might be different. With Original Medicare plus Medigap, your parent has predictable monthly premiums and low or no copays. With Medicare Advantage, the monthly cost is low but the copays might be higher, and the doctor network is restricted.

Over a decade, these costs are roughly similar for people with average healthcare expenses. The choice comes down to flexibility and peace of mind versus cost savings and extra benefits.

If your parent values seeing any doctor they want and doesn't like surprises or dealing with insurance company approval processes, Original Medicare plus Medigap is worth the extra monthly cost.

If your parent is relatively healthy, has few established doctors, and doesn't mind the Medicare Advantage model, the lower premiums make sense.

The thing nobody tells you is that most people don't stay on the same plan for 20 years. Healthcare needs change. Plans change. Life happens. The decision you make at 65 doesn't have to be the decision you make at 75. You can switch during Annual Enrollment every October. You can change your strategy. You can adapt.

What matters is understanding what each choice actually means, and making that first choice during the window when you have the most freedom and the best financial terms. That window closes after 63 days from Part B enrollment, and your parent is living with the consequences for decades.

How To Help Your Elders is an educational resource. We do not provide medical, legal, or financial advice. The information in this article is general in nature and may not apply to your specific situation. If you are concerned about a loved one's cognitive health or safety, consult with their healthcare provider or contact your local Area Agency on Aging for guidance and support.