HL7 ADT Message Example: MSH, EVN, PID and PV1 Explained
ADT messages are some of the most common HL7 v2 messages in hospital integration. They carry patient admission, discharge, transfer, registration, and demographic update events.
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Synthetic HL7 ADT A01 message
MSH|^~\&|SYNTH_EHR|FAKE_HOSPITAL|ADT_RECEIVER|DEMO_CLINIC|20260601143000||ADT^A01|MSG00001|P|2.5.1 EVN|A01|20260601143000 PID|1||DEMO0001^^^MRN^MR||EXAMPLE^ALEX^A||19800101|U|||100 SAMPLE ST^^TESTVILLE^IL^00000||(000)000-0000 NK1|1|EXAMPLE^CONTACT|SPO|100 SAMPLE ST^^TESTVILLE^IL^00000 PV1|1|I|UNIT^101^1||||0001^DEMO^DOCTOR|||||||||||VISIT0001
This example is synthetic and safe for demonstration. It shows the shape of a typical ADT A01 admission message without representing a real patient, facility, or provider.
| Segment | Purpose | What to inspect |
|---|---|---|
| MSH | Message Header | Sender, receiver, timestamp, message type ADT^A01, control ID, HL7 version |
| EVN | Event Type | Trigger event and event date/time |
| PID | Patient Identification | Synthetic patient identifier, name, date of birth, sex, and demographics |
| NK1 | Next of Kin | Emergency contact or associated party details when present |
| PV1 | Patient Visit | Patient class, location, provider, and visit number |
How to read the ADT message
Start with MSH-9. The value ADT^A01 means the message is an ADT admission event. MSH-10 is the message control ID used for tracking and acknowledgements. MSH-12 identifies the HL7 version. EVN confirms the trigger event and timestamp.
PID carries patient identity. In production messages, this can include PHI such as medical record numbers, names, dates of birth, addresses, and phone numbers. PV1 carries visit context: inpatient or outpatient class, assigned location, attending provider, visit number, and related admission data.
Common ADT parsing use cases
- Confirming a registration feed is sending the expected ADT event code.
- Checking whether patient identifiers arrive in PID-3 with the expected assigning authority.
- Inspecting PV1 visit and location fields before warehouse mapping.
- Training interface analysts on admission and discharge message structure.
- Reviewing synthetic examples before testing with approved real data.
Parse the example
Paste the synthetic message into the parse HL7 ADT messages workflow to inspect fields and components. For a deeper reference, use the HL7 segment guide to compare MSH, EVN, PID, NK1, and PV1 fields.
Frequently Asked Questions
What is an HL7 ADT message?
An HL7 ADT message communicates admission, discharge, transfer, registration, and patient update events between healthcare systems.
Which segments are common in ADT messages?
Common ADT segments include MSH, EVN, PID, NK1, PV1, PV2, AL1, DG1, and sometimes IN1 depending on the workflow.
Can I parse ADT messages online?
Yes. You can use a browser-based HL7 parser to inspect synthetic or authorized ADT messages and review segment and field structure.