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Health insurance wasn't enough to spare a high school teacher from a $108,951 hospital bill. Drew Calver, 44, of Austin, Texas, had a heart attack last year, resulting in a four-day emergency hospital stay, according to a report from Kaiser Health News. Despite having health-care coverage, he wound up with the six-figure bill — thanks to a practice known as "balance billing." In balance billing, medical providers that are out of network are unable to reach an agreement with the insurer on a reasonable price for service. In turn, the patient ends up on the hook for the remainder. Patients often also end up with higher expenses in the form of high deductibles, out-of-network fees and additional expenses related to testing that may not be useful. Your best protection is to become an empowered patient and prepare to contest unreasonably high bills. Here are four suggestions from Carolyn McClanahan, a certified financial planner and an M.D., to gear up for battle.

1. Ask the right questions

It's no longer enough to ask your doctor's receptionist, "Will you take my insurance?" "When you're making an appointment, don't ask if you're covered under your plan," said McClanahan, who is director of financial planning at Life Planning Partners in Jacksonville, Florida. "Everyone will take your insurance." Your doctor's office may accept your insurance, but that won't spare you from a surprise bill weeks later if he or she is out of your network, McClanahan said. The correct question for your doctor's receptionist is, "Are you in my network?" Be sure to document who gave you the answer and the date so that you're prepared to fight back if you get a bill that says otherwise, McClanahan said. Speak up when your doctor recommends tests and prescriptions. Ask questions such as: "Is the testing facility in-network?" or "Are the doctors evaluating the tests in-network?" Recent data from the Kaiser Family Foundation showed that nearly 1 in 5 inpatient hospital admissions include a claim from an out-of-network provider. The foundation studied medical bills from large employer plans.

Don't be shy about asking your doctor for an explanation if he or she recommends that you undergo a test. Learn more about the test and find out how the results will affect the approach to treatment. "If they can't provide a clear answer, ask, 'Is this test really necessary?'" said McClanahan. Finally, curb costs on prescriptions by asking whether your medication is covered under your plan and if a cheaper version is available. Sometimes it's cheaper to pay cash for your medication than to claim it on your insurance, McClanahan said. She suggested digging up drug price information on GoodRx.com and comparison shopping. "Know the benefits and risks, how long will you be on medication, and what are the alternatives to the medication prescribed," McClanahan said.

2. Examine your plan's coverage

Understand what your policy covers, including the details on out-of-pocket maximums, deductibles and coinsurance. Get familiar with your state's laws against balance billing. More than 20 states have some kind of legislation on the books to protect consumers from balance billing, according to the Commonwealth Fund.

When you are admitted to the hospital in the event of an emergency, write on all of your paperwork that you will only permit in-network care, said McClanahan. Be sure to take a photo of this document or make a copy of it. "Once you get the bill, if they charge you for out-of-network care, you have ammunition," McClanahan said.

3. Fight back

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If balance billing is illegal in your state and you receive a massive out-of-network bill, be sure to reach out to your doctor first, as it may be an error. Pull in your insurer to help. If neither your doctor nor your insurer will help you address the bill, then it's time to contact the regulators, said McClanahan. That means you should reach out to your state medical board and your state's insurance department. If your insurance plan is self-funded – one in which your employer assumes the financial risk for providing your health-care benefits – then you should contact the U.S. Labor Department's Employee Benefits Security Administration.

4. Keep good records