Patients and their families are rarely told when hospitals make mistakes with their medicines, according to a new study.

Most medication mistakes did not harm patients, the researchers found, but those that did were more likely to happen in intensive care units. And ICU patients and families were less likely to be told about errors than patients in other hospital units.“For the most part, our findings were in keeping with what the existing literature tells us about the where and how of medication errors in a hospital,” wrote Asad Latif, an assistant professor at Johns Hopkins University School of Medicine and the study’s lead author, in an e-mail. “The most surprising finding was what we do about them, at least in the immediate time around when they occur.”

Read More: The Washington Post