An electronic health record (EHR) refers to an individual patient’s medical record in digital format. Electronic health record systems co-ordinate the storage and retrieval of individual records with the aid of computers. EHRs are usually accessed on a computer, often over a network. It may be made up of electronic medical records (EMRs) from many locations and/or sources. Among the many forms of data often included in EMRs are patient demographics, medical history, medicine and allergy lists (including immunization status), laboratory test results, radiology images, billing records and advanced directives.