A medical error is an unexpected and undesired event (adverse
event) that results directly from the health care or services you receive but
which could have been prevented.
Errors may happen when a health professional fails to complete a
planned action or treatment as it was intended, or uses an incorrect plan for
an action or treatment, such as giving a patient the wrong medicine or dose or
giving someone a medicine they are allergic to. Errors can also happen when
medical equipment or devices are used incorrectly. Errors may also happen when
medical equipment or devices fail. Adverse events, whether due to a medical
error or not, are not complications of disease or expected side effects of
medicines or other treatments. An adverse event may result in injury or
How this information was developed to help you make better health decisions.