Many seniors are shocked to learn that healthcare coverage under Medicare is by no means free. Quite the contrary -- there are numerous costs associated with Medicare, from monthly premiums to annual deductibles to coinsurance and copays. And when you're on a fixed income, which is the case for many Medicare patients, those costs can be an enormous burden.

It's not surprising, then, to learn that 63% of Medicare enrollees worry about surprise bills following medical treatment, according to a new survey by online health insurance exchange eHealth. If that's a concern for you, here are a few things you can do.

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IMAGE SOURCE: GETTY IMAGES.

1. Understand your built-in costs

Generally speaking, when you receive care under Medicare Part B, which pays for everything from doctor visits to diagnostic tests to durable medical equipment, Medicare will cover 80% of the cost, leaving you to pick up 20% of the tab. This assumes, however, that the service in question is a covered service. If it isn't, you could get stuck with the entire bill. If you're not sure whether your service is covered, ask. It's an easy way to avoid unpleasant surprises.

Another thing: When you're admitted to a hospital under Medicare Part A, you'll be subject to a deductible that can change from year to year. Currently, that deductible is $1,408. In exchange, you pay nothing other than that deductible for your first 60 days in a hospital, but from there, your next 30 days will cost you $352 each. Knowing what costs you're liable for will help you plan accordingly so that when you start getting bills, they aren't shocking.

2. Get supplemental insurance

Clearly, there's a host of expenses you might encounter under Medicare. A good way to minimize them is to purchase supplemental insurance known as Medigap. Medigap can pick up the tab for deductibles and copays so you're not left to cover those bills alone. That said, Medigap won't pay for services that Medicare itself won't cover, so you'll still need to account for those costs yourself. For example, Medicare won't pay for dental exams, hearing aids, or vision tests. If you need these services, you'll continue to pay out of pocket even if you have Medigap coverage in place.

3. Sock away funds for future healthcare expenses

If you're not yet retired but are worried about affording healthcare under Medicare once you do leave the workforce, make an effort to contribute to a health savings account, or HSA. With an HSA, your contributions go in tax-free, so there's instant savings involved. You can then withdraw funds as you need them for immediate medical expenses, or invest the funds you're not using and carry them into retirement, when healthcare can eat up even more of your budget.

You're eligible for an HSA if you're enrolled in a high-deductible health insurance plan. For 2020 purposes, that means an individual deductible of $1,400 or more, or a family deductible of $2,800 or more. If you qualify, you can contribute up to $3,550 to an HSA this year as an individual, or up to $7,100 on behalf of a family. And if you're 55 or older, you get a $1,000 catch-up contribution on top of these limits, similar to the catch-up provision you'll find in popular retirement savings plans like IRAs and 401(k)s.

Though Medicare offers critical health benefits to millions of seniors, the costs you encounter under it could be quite substantial. If unplanned bills under Medicare are a concern for you, read up on how your benefits work, get supplemental insurance, and, if you're not yet retired, set aside money in an HSA. Doing so could help you avoid a world of financial and emotional stress at a time in life when you deserve better.