A lot. The majority of personal bankruptcies are due to medical bills, according to a 2013 study by NerdWallet Health. More than one in five people had difficulties paying their medical bills in 2013, while three out of five personal bankruptcies were due to medical bills [source: Lamontagne]. And these figures include those with health insurance along with the uninsured. All it takes is one major illness or injury to wreak havoc on your personal finances, even if you have a decent amount of savings and little or no debt.
A few sobering statistics: About 56 million Americans under age 65 have trouble paying their medical bills. More than 11 million Americans aged 19 to 64 will be forced to take on pricey credit card debt to pay their hospital bills. Some 10 million Americans aged 19 to 64 with year-round insurance still won't be able to pay their medical bills. And nearly 2 million Americans live in households that will declare bankruptcy due to medical bills [source: Lamontagne].
Clearly, this is a major problem. People generally can't help it if they incur staggering medical bills. Yet if someone files for bankruptcy, that's just the start of his problems. Filing for bankruptcy will, in turn, negatively affect a credit score for up to 10 years, result in much higher interest rates for credit, and make it more difficult to rent property. He may even lose out on job opportunities [source: Austin].