It's the quintessential American nightmare. You may have health insurance, or you may not. But millions of Americans each year end up buried in medical bills, forcing some to declare bankruptcy. In fact, medical debt is the leading cause of bankruptcy in the U.S.

A study conducted by NerdWallet says that one in five Americans will be contacted by a debt collection agency about medical bills this year. It estimated that nearly 17 million adults (19 to 64) received a lower credit rating because of medical bills in 2013. And while the Affordable Care Act has provided insurance to many more Americans, many others cannot afford new higher deductibles and may already be carrying prior medical debts that the new program does not address.

A recent survey of 1,006 Americans by Bankrate.com found that one in four people say their medical debt exceeds their emergency savings. The problem is even more desperate among low-income people; nearly half (44%) of those earning below $30,000 per year have medical debt that eclipses their emergency savings, according to the Bankrate survey.

What should you do if you're worried that medical bills could be overwhelming your ability to keep up with them? Here are three important places to start.

Read Your Bills Carefully

While some people feel their only or best option is to immediately file for bankruptcy, the first step, says Adria Goldman Gross, of Monroe, NY, CEO and founder of MedWise Insurance Advocacy and MedWise Billing, Inc., is to see why your claims aren't getting paid." Are you getting such high bills because something hasn't been done? "You have to find out why a claim is not being processed," she says. "Was it denied? Did you not get authorization? Is it an out-of-network provider? Were you billed incorrectly? You might also have a wrong diagnosis code and/or procedure code, she explains.

Like most such advocates, Gross charges an hourly fee to review medical bills, usually $75 to $150 per hour, plus one-third of the savings she is able to acquire as a result of her review. I can tell pretty quickly if I can get it resolved, she says.

The worst move, Gross says, is the most common: People ignore the bills – ignore, ignore, ignore – and when it goes into collections, you're really screwing yourself. It's easier to negotiate with a provider than with a collection agency. Challenge bills that seem incorrect, but be sure to respond to them. If they are accurate, try to set up a payment plan so you aren't on the record as delinquent.

Gross cautions everyone who has purchased health insurance to be sure their premiums are completely up to date. Insurance companies set up payment plans, but they may not claim the money and the payments are not being taken out while the consumer assumes that they are. Make sure your premiums are paid for! I must get five calls about this problem a week. Read your plan very carefully.

Understand Your Plan

You need to understand your plan, agrees Kevin Lucia, a senior research fellow with the Center on Health Insurance Reforms at Georgetown University. There's a low level of health insurance literacy, and these contracts are complicated legal devices that aren't easy to navigate. You have to know what your financial risks are. Many people simply assume that their medical insurance will pay for their medical needs.

Protecting yourself from the possibility of crippling medical debt means being a savvy and curious consumer, Lucia says. Understand the product you're buying and make sure what you're buying meets your needs.

The Affordable Care Act, he adds, does not offer guaranteed protection against medical debt, because cost-sharing – i.e. forcing patients to pay for services they did not choose or even want, such as an out-of-network physician – remains a problem for anyone with insurance. Co-pays and high deductibles can cost anyone thousands of unexpected dollars, so keeping an emergency savings fund is wise, he says.

Check in Advance

One route, if possible – your procedure is not an emergency – is to do your best to check in advance that everyone involved in an upcoming procedure is covered under your network. For example, you could be in an in-network hospital using a surgeon who is in your network, but find that the anesthesiologist assigned to the operation is not.

Also make sure that you know everyone who will be at the operation. There is a scheme called "drive-by doctoring," in which you could find that you are being billed by an "assistant surgeon" you didn't know would be part of the procedure. Another name for this practice is "balance billing." New York State has just passed a Surprise Bill Law, which goes into effect on March 31, 2015, to address such abuses. It is one of only 13 states with similar protections.

It's very difficult once the bills start to stop the process, Lucia warns. Providers can be quite aggressive when collecting and people who are sick are not in a position to push back. It's really difficult to climb out of debt or walk away from it, from a legal perspective.

The Bottom Line

Health insurance contracts are complicated and legally binding documents. Read the small print carefully and keep an emergency fund in case of co-pays and to meet high deductibles.

To learn more about bankruptcy and its consequences, read When To Declare Bankruptcy, File Chapter 7 Bankruptcy and The Other Personal Bankruptcy Option: Chapter 13.