"between 210,000 and 440,000 patients each year who go to the hospital for care suffer some type of preventable harm that contributes to their death"
http://www.propublica.org/article/how-many-die-from-medical-mistakes-in-us-hospitals
Harm from medical care is a very big problem. Many hospitals are amazingly incompetent, failing to institute basic care guidelines that would save a lot of lives. If you have any choice about what hospital to go to, try to find information about the medical accident rate there. This will be difficult; hospitals always try to hide any information that could be used to judge their quality.http://www.propublica.org/article/how-many-die-from-medical-mistakes-in-us-hospitals
In general, medical care is both more dangerous and less effective than most people think. This new study is evidence that going to a hospital is more dangerous than we thought it was.
However, it does not mean that they 'kill' over 200,000 people. It does not even mean that all of those people would be alive today if they had done everything perfectly. It means that those people died, and somewhere in their medical records was a mistake that could have been bad. The number of people actually killed by these mistakes is likely to be a small percentage of the 210,000 to 440,000 guess. Even then, many of the mistakes were ones of omission, where the doctors missed something they should have caught. In such cases, staying away from medical care would clearly not have saved the life of the victim.
But still, if you do not really need advanced medical care, it is usually wise to stay away from hospitals.