HL7 ADT^A01 (Admit / Visit Notification)
ADT^A01 notifies systems that a patient has been admitted as an inpatient (or has started a visit). It establishes a new encounter and carries the patient’s current demographics and visit assignment.
When is ADT^A01 sent?
Sent by the ADT/registration system at the moment of inpatient admission, after a bed/location is assigned.
Key segments
The segments below are the ones most relevant to ADT^A01. Real messages may carry additional optional segments depending on the sending system’s configuration.
| Segment | Usage | Role |
|---|---|---|
| MSH | Required | Message header: sending/receiving application & facility, message type, control id, version. |
| EVN | Required | Event type: the trigger event code and the date/time the event occurred. |
| PID | Required | Patient identification: identifiers (MRN), name, date of birth, sex, address, phone. |
| PV1 | Optional | Patient visit: patient class, assigned location, attending provider, admit/discharge details. |
Example ADT^A01 message
A realistic, well-formed example. Segments are separated by carriage returns; fields by the pipe (|) delimiter.
MSH|^~\&|EPIC|HOSP|REC|REC|20240115093045||ADT^A01|MSGCTRLA01|P|2.5.1
EVN|A01|20240115093045
PID|1||MRN12345^^^EPIC^MR||DOE^JOHN^A||19800101|M|||123 MAIN ST^^CITYTOWN^WA^98101||555-555-0100
PV1|1|I|ICU^101^AMapping ADT^A01 to FHIR
See the full field-by-field mapping of ADT^A01 to a FHIR Patient — including the transforms and gotchas — on the ADT^A01 → US Core Patient reference page. You can fork that template and run it in the Mapping Builder.
Frequently asked questions
What is an HL7 ADT^A01 message?
ADT^A01 is an ADT (Admit, Discharge, Transfer) message with trigger event for admit / visit notification. It carries patient demographics (PID) and usually visit details (PV1) so downstream systems stay in sync with the patient's state.
Which segments does ADT^A01 contain?
At minimum MSH (header), EVN (event), and PID (patient identification). Most ADT^A01 messages also include PV1 (patient visit). Additional segments such as NK1, AL1, DG1 or IN1 may follow depending on the sending system's configuration.
How do I convert ADT^A01 to FHIR?
Map the PID demographics to a FHIR Patient (and PV1 to an Encounter). Identifiers need a real system URI, dates need ISO-8601 reformatting, and coded values like sex need a value-set lookup. You can do this with the Interoperall mapping tools.
How do I validate a ADT^A01 message?
Paste the raw message into the HL7v2 validator to parse each segment, check the structure, and get a compliance score. It runs entirely in your browser, so PHI never leaves your device.