When people go to a hospital, they assume the medical professionals there will treat their illnesses skillfully, and they will return home in better health than before they left.

Sadly, this is not always the case. In fact, sometimes patients not only leave with new ailments and must be readmitted, but an unfortunate number die from their hospitalization.

According to a 2010 government study, published by Consumer Reports, “mistakes and other medical harm contribute to an estimated 15,000 deaths each month. And that’s just among Medicare patients.”

The nonprofit organization analyzed data from more than 1,000 hospitals across 44 states and found that “some hospitals pose more risk than others, although bad things can happen at even the best hospitals.”

The report also claims that “many of the medical mistakes that occur in hospitals are not reported, so we only know about a fraction of the errors that occur.”

To help its readers assess the safety of their hometown hospitals, Consumer Reports gave each hospital a rating in several categories, including preventing infections, reducing readmissions after discharge, clear communication about medications and discharge, and reducing overuse of CT scans.

Of the categories, the AARP, an organization for people 50 and over, focuses on readmissions. The group reported, “For Medicare patients, one in five is re-hospitalized within 30 days, one in three within three months.”

AARP says there are things people can do to avoid a return trip to the hospital. “Many readmissions, which cost the health care system billions, are preventable,” they say. Suggestions include “Teach-back,” which means hearing instructions and then repeating them back to hospital staff over a few days. This helps patients remember directions for medications, treatment and care.”

Also, “Get clear written and oral instructions about what to take, what not to take, and when and how to take medicines… you need another person with you to ask questions and make sure you understand.”