. I heard that in 2008 62% of all personal bankruptcies in the US were due to medical bills and 50% of those people actually had insurance.
The "medical bankrutpcy" issue is complex.
Maybe there are more recent figures, but the message about medical bills causing most bankruptcies started with a Harvard study from 2005. The study abstract said:
"In 2001, 1.458 million American families filed for bankruptcy. To investigate medical contributors to bankruptcy, we surveyed 1,771 personal bankruptcy filers in five federal courts and subsequently completed in-depth interviews with 931 of them. About half cited medical causes, which indicates that 1.9-2.2 million Americans (filers plus dependents) experienced medical bankruptcy. Among those whose illnesses led to bankruptcy, out-of-pocket costs average $11,854 since the start of illness; 75.7 percent had insurance at the onset of illness. Medical debtors were 42 percent more likely than other debtors to experience lapses in coverage. Even middle-class insured families often fall prey to financial catastrophe when sick."
The full report: MarketWatch: Illness And Injury As Contributors To Bankruptcy -- Himmelstein et al., 10.1377/hlthaff.w5.63 -- Health Affairs
When this study came out some conservatives claimed that it was a myth that bankruptcies are often caused by medical problems and cited their own review through the US Trustee's office of bankruptcy petitions which showed 78% of bankruptcy petitions show medical debt of less that $5000. (sorry, I have since lost the citation).
However, the US Trustee's review tells only part of the story. First of all, there are plenty of people that have so little that garnishment of wages resulting from a $5000 medical bill can send them into bankruptcy. Also, even if medical bills are paid by insurance, the medical problems can mean loss of time from work that might not be paid or even the loss of a job. Also, people live on such tight budgets that the slightest little slip can mean a bankruptcy. So, it is a muddy analysis but medical issues, both bills and illness, do contribute to bankruptcy filings. Along with job loss, divorce and living on the edge.