Medigap: extra insurance for your share of Original Medicare costs

Original Medicare pays for a lot, but not everything. What is left over is your share of covered services. That leftover part is the gap, and it is the part Medigap is built to shrink.

Medicare.gov describes Medigap as extra insurance you can buy from a private insurance company to help pay your share of out-of-pocket costs under Original Medicare. It names three costs directly: copayments, coinsurance, and deductibles.

That is the whole idea. Medigap does not add new benefits or cover new services. It sits behind Original Medicare and picks up part of what you would otherwise pay yourself.

Medigap is not a second insurance plan. Think of it as a cushion under the one you already have.

Cost sharing that feels small once a year feels very different when it repeats. Cancer care often means frequent appointments, repeated imaging, months of treatment, and sometimes a hospital stay too.

Each of these carries your share of the cost. One bill alone is manageable. Add them all up, and the total gets heavy. This is why many people start looking at supplemental coverage right after a diagnosis, not before.

To buy a Medigap policy, you must have both Part A (hospital insurance) and Part B (medical insurance).

This rule tells you something about how Medigap works. It is built to sit alongside Original Medicare. If you are looking at Medicare Advantage instead, you are looking at something different entirely. That is a private plan bundling your coverage together, not a supplement sitting behind it, so the two options are not really interchangeable.

Medigap policies are sold by private companies, so the market matters. A few steps worth taking:

• Compare quotes from several companies rather than accepting the first one.
• Read the Medigap basics section on Medicare.gov before talking to any salesperson.
• Get clear on what problem you are solving. Steady costs across a long treatment course is different from planning for one expected hospital stay.
• Ask directly how drug costs fit in, since prescription coverage runs through Part D, not through Original Medicare itself.

Anything a broker tells you beyond what Medicare.gov says is worth double-checking. Call 1-800-MEDICARE or your State Health Insurance Assistance Program before you sign anything.

Two sources of unbiased help are worth using. Your State Health Insurance Assistance Program gives free counselling on Medicare choices. Most cancer centers also have financial counsellors or social workers who have guided many patients through this. They can tell you which costs actually add up in your kind of treatment.

Bring real numbers to these conversations. What have you already spent this year? What does your treatment plan look like going forward? Is your care mostly outpatient, or likely to involve hospital stays?

Medicare.gov's overview of Medigap is short. It explains what Medigap is, the three cost categories it helps with, and the requirement to have Parts A and B. It does not spell out exclusions, pricing, or how it works with Part D on that page.

So treat this article as a starting shape, not the full picture. The details that decide whether a policy is right for you live in the actual policy documents and the Medigap basics material. Reading them before you commit is worth the time, because coverage decisions made during treatment are hard to undo later.