HL7 v2Health Level Seven Version 2
In short
HL7 v2 is the messaging standard that hospital systems have used for decades to notify each other of admissions, orders and results. HL7 International describes it as one of the most widely implemented health standards in the world, and it coexists with FHIR rather than having been replaced by it.
- Type
- Standard
- Steward
- HL7 International
- Current version
- 2.9.1 (ANSI/HL7 V2.9.1-2024)
- Reviewed
- October 25, 2026
Explanation
What it is
HL7 Version 2.x is HL7 International's messaging standard for exchanging clinical and administrative data between systems. The first version came out in October 1987, and, as of October 2026, the latest is 2.9.1, approved as an ANSI standard in September 2024 (ANSI/HL7 V2.9.1-2024), revising 2.9 from 2019. HL7 describes it as one of the most widely implemented health standards in the world: according to the organization, 95% of US healthcare organizations use it and it has implementations in more than 35 countries.
How it works
A v2 message is triggered by an event (an admission, an order, a result) and is made of segments, each on its own line, with fields separated by vertical bars (|):
- MSH: header with sender, receiver, message type and version.
- PID: patient data.
- OBR and OBX: the order and each observed result.
The message type combines a code and an event, for example ADT^A01 (admission) or ORU^R01 (results).
Why it is still current
- Versions are generally backward compatible, so a 2.3 system and a 2.5.1 system can coexist with clear rules.
- Mature implementation guides exist, for example for reporting laboratory results to public health in the US.
- According to HL7, v2 supports the majority of the common interfaces used in the healthcare industry globally.
Common misconceptions
- "Speaking HL7" is not enough. HL7 presents v2 as a framework for negotiating what the standard does not fix, so every interface needs an agreed specification of version, events, fields and code tables.
- v2 is not just "HL7": HL7 also publishes CDA and FHIR, which solve other problems.
- Moving to FHIR does not require switching v2 off. In 2025 HL7 published an official guide (STU 1.0.0) for mapping v2 messages to FHIR resources.
Usage examples
In the US, HL7 publishes a v2.5.1 guide for electronic laboratory reporting of results to public health (Electronic Laboratory Reporting).
HL7 also publishes a v2.5.1 syndromic surveillance guide for the US, which defines how to send that data to public health.
HL7 distributes message profiles for Germany based on version 2.5 (German Message Profiles for HL7 Version 2.5).
The HL7 Version 2 to FHIR guide (STU 1.0.0, 2025) publishes maps for messages such as ADT_A01 (admission) and ORU_R01 (results) to FHIR resources.
In the US, HL7 publishes the v2.5.1 Laboratory Results Interface (LRI) guide, Edition 5, for sending laboratory results to the health record.
The admissions system tells the laboratory and imaging that a patient has been admitted, with an ADT^A01 message.
The laboratory information system sends results to the medical record as ORU^R01 messages, with one OBX segment per analyte.
Relation to other terms
Relies on0
This term does not rely on other glossary terms.
Depend on this one3
- IHEStrong
Many IHE profiles, especially in radiology, laboratory and IT infrastructure, specify their transactions with HL7 v2 messages.
- DICOMMedium
In imaging workflows, orders and patient data usually reach the RIS through HL7 v2 before becoming the DICOM worklist.
- MPI / EMPIMedium
The IHE PIX and PDQ profiles, which feed and query an MPI, are based on HL7 v2 messages; HL7 v3 and FHIR variants also exist.