Findings from a new University of California San Diego study lend credence to what is called the "July effect" -- a long-held suspicion that July is the most dangerous month to go to the hospital.
It's the time when teaching hospitals take on an influx of new medical residents, most of whom have little previous experience.
"There is the turnover of staff. And that's a time when people are just learning, and mistakes can be made," said Dr. Richard Besser, Senior Health and Medical Editor for ABC.
And even a seemingly tiny mistake can be fatal, particularly when it comes to medication.
Researchers looked at 20 years worth of death certificates, from about 62 million patients, and found a trend: The number of deaths caused by medication errors remained steady for 11 months of the year, but spiked in July.
In teaching hospitals where interns were more likely to be assigned, patients were more likely to die from errors in their medications in the month of July, ABC reported.
Experts suggest a few steps that patients, and friends and family of patients, should take to assure a safe hospital visit.