Many individuals and families in Illinois and elsewhere across the country know — either anecdotally or from painful personal experience — that medical debt is a prime catalyst driving further financial difficulties.

And here’s a singular and especially problematic matter to note about medical debt and its close nexus with material financial challenges: It often proves to be impervious to good planning, because it emerges suddenly and in a completely unexpected way.

Oh, and one more thing: When it does become an issue for many people, it tends to be a top-dollar concern, coupled with complexities surrounding providers, network-relates issues, deductibles, out-of-pocket costs and other matters.

Much of those thorny considerations are prominently noted in a recent national media piece chronicling a medical debt-related problem that is of special significance for older Americans, specifically those about to become eligible for Medicare services.

Imagine that you dutifully and timely do everything required to enroll in the traditional Medicare program. You then undergo a surgery that you know is covered under Medicare, with most of the costs defrayed.

Then you get a bill for many thousands of dollars. It turns out that the private insurer you were with prior to transferring to Medicare automatically enrolled you in its own variant form of the government program, called Medicare Advantage. Unbeknownst to you, you approved of that outcome when, after receiving a mailing regarding the details, you did not opt out of acceptance within a stated period.

Such insurer action is becoming increasingly commonplace across the country, its rationale being that it makes the transfer to Medicare a simpler and more “seamless process.” Indeed, the federal program endorses it, provided a claimant does not opt out.

The problem, of course, is that many people don’t even know that they have opted in, believing, instead, that they are insured under the traditional program.

Not knowing the reality can cost an individual a huge amount of money. What’s covered under traditional Medicare might not be treated exactly the same under Medicare Advantage. An in-network doctor under the former program might be deemed out of network by Medicare Advantage, with a claimant unknowingly accepting services at a highly marked-up rate.

Medical bills always spell problems for many Americans. With something like Medicare Advantage, the potential for a material financial challenge to arise increases markedly.