Approximately 1.3 million people are injured annually in the United States following a medication error. The National Coordinating Council for Medication Error Reporting and Prevention defines a medication error as "any preventable event that may cause or lead to inappropriate medication use or patient harm while the medication is in the control of the health care professional, the patient, or consumer related to professional practice".

The U.S. Food and Drug Administration(FDA) currently reviews medication error reports that come from drug manufacturers and through MedWatch, the agency's safety information and adverse event reporting program. The agency also receives reports about medication errors from the Institute for Safe Medication Practices (ISMP) and the U.S. Pharmacopeia.

The American Hospital Association lists the following as some common types of medication errors:

• Unavailable drug information (such as lack of up-to-date warnings)
• Lack of appropriate labeling as a drug is prepared and repackaged into smaller units
• Miscommunication of drug orders, which can involve poor handwriting, confusion between drugs with similar names, misuse of zeroes and decimal points, confusion of metric and other dosing units, and inappropriate abbreviations
• Incomplete patient information (not knowing about patients' allergies, other medicines they are taking, previous diagnoses, and lab results, for example)
• Environmental factors, such as lighting, heat, noise, and interruptions, that can distract health professionals from their medical tasks