I've seen tons of medical charts in my time..

"Doctors' sloppy handwriting kills more than 7,000 people annually. It's a shocking statistic, and, according to a July 2006 report from the National Academies of Science's Institute of Medicine (IOM), preventable medication mistakes also injure more than 1.5 million Americans annually. Many such errors result from unclear abbreviations and dosage indications and illegible writing on some of the 3.2 billion prescriptions written in the U.S. every year."

http://www.time.com/time/health/article/0,8599,1578074,00.html