You could get caught owing many thousands of dollars even though I have sold you the best coverage available. This is due to two little words in your hospital medical chart – “Under observation”. Make sure that if you go to the hospital and stay there, that you are actually “admitted.” NBC News explains it in this two words can cause medicare patients thousands of dollars video.
Here is another video created by Ronald Hirsch that explains the details of these rules. Ask to be admitted as an inpatient- The real rules.
Update 2018: This is still a major problem today. The laws now require hospitals to give formal notification of status change. However, it is a form and it is seldom read or understood. A nurse will just ask you to sign that you have received the paper. Your nurse may not even know the implications of moving you to observation status.