HL7 v2 Reference Guide
HL7 v2 is the backbone of clinical data exchange — ADT events, lab orders, results, documents, and pharmacy messages that move between HIS, EHR, LIS, RIS, and billing systems across every major hospital.
HL7 Message Guides
116 guides covering common message types and integration patterns.
HL7 Segments
173 segments — the named field groupings that make up every HL7 v2 message.
HL7 Data Types
69 data types — the field-level building blocks used across every segment.
HL7 Code Tables
79 code tables — the standardized value sets referenced by HL7 v2 fields.
Transport Methods
How HL7 v2 messages move between systems — MLLP, HTTPS, and the rest.
HL7 Transport: Minimal Lower Layer Protocol
MLLP is the de-facto standard for HL7 v2 message transport, using TCP-based persistent connections with byte-framing.
Read lesson →HL7 Transport: Raw TCP/IP
Unframed TCP/IP transport for HL7 messages without MLLP framing; requires application-level message boundary handling.
Read lesson →HL7 Transport: SFTP Batch Files
Asynchronous batch HL7 message transport via SSH File Transfer Protocol with file-based polling and atomic write patterns.
Read lesson →HL7 Transport: Shared Folder / File-Drop
Legacy file-sharing transport for exchanging HL7 v2 messages via SMB/CIFS or NFS shares with polling and batch envelope segments.
Read lesson →HL7 Transport: HL7 over HTTPS/REST
HTTP POST and REST APIs for transporting HL7 v2 and FHIR messages using TLS-secured endpoints.
Read lesson →HL7 Transport: SOAP Web Services
SOAP envelopes carrying HL7 v2 messages over HTTP/HTTPS with WSDL service definitions and WS-Security.
Read lesson →Frequently Asked Questions
What is HL7 v2?
HL7 v2 is the most widely deployed healthcare messaging standard, using pipe-delimited text to let EHRs, labs, pharmacies, and imaging systems exchange real-time patient data. It predates FHIR and remains dominant in hospital environments globally.
What are the most common HL7 v2 message types?
The most common HL7 v2 messages are ADT (patient events), ORU (lab and clinical results), ORM (orders), and MDM (documents). ADT messages alone drive the majority of real-time notifications across hospital EHR and ancillary systems.
What is an HL7 segment and what do the most common ones do?
An HL7 segment is a named, pipe-delimited line grouping related fields. Key segments: MSH (header/routing), PID (patient identity), PV1 (visit info), OBX (observations/results), ORC (order control), and NTE (notes). Each message type defines which segments are required.
How is HL7 v2 transported between systems?
HL7 v2 is most commonly transported via MLLP over TCP/IP for real-time feeds or SFTP for batch delivery. Modern integration engines including Vorro also support tunneling HL7 v2 payloads over REST HTTP endpoints for cloud-to-cloud connectivity.
What is the difference between HL7 v2 and FHIR?
HL7 v2 uses pipe-delimited text over MLLP and dominates real-time clinical messaging in hospitals. FHIR uses JSON/XML REST APIs and is mandated for patient access under the 21st Century Cures Act. Many organizations run both standards simultaneously.
Which integration engines support HL7 v2 message processing?
Major HL7 v2 integration engines include Vorro, Mirth Connect (NextGen), Rhapsody Health, Cloverleaf, and Boomi. Vorro differentiates with healthcare-native routing and transformation that handles common message types without custom scripting.
How do I validate an HL7 v2 message?
Validate HL7 v2 by confirming the MSH segment is well-formed, required fields are populated, segment order matches the message structure spec, and data types are correct. Vorro's integration engine includes built-in validation, error alerting, and message inspection tools.
What does an HL7 ADT message look like?
An HL7 ADT message begins with an MSH header, followed by an EVN (event type) segment, PID (patient identity), and PV1 (visit details). For example, an A01 admit triggers downstream notifications to lab, pharmacy, and billing systems automatically.
