HL7 v2 vs FHIR, actually
9 min read
You will hear both terms in your first month and nobody will stop to define either one. Here is the whole picture, in the order you will actually encounter it.
HL7 v2 came first, and it is still everywhere
HL7 Version 2 is a messaging standard from the late 1980s. It moves data between systems as pipe-delimited text segments: MSH|^~\&|SENDING_APP|.... An ADT message tells a downstream system a patient was admitted. An ORU message carries a lab result. Every major EHR still speaks it, mostly for interfaces between systems that predate the web.
It is not pretty, and it does not need to be. It is stable, well understood by every integration engineer who has touched a hospital network, and it is not going anywhere in your career.
FHIR is the API version
Fast Healthcare Interoperability Resources represents the same kinds of data (patients, observations, medications) as JSON or XML resources, exchanged over standard web APIs. If you have used any REST API, FHIR will look familiar almost immediately: GET /Patient/123, POST /Observation.
FHIR is what new interoperability work is built on, and it is the standard behind most of what you will hear called "patient access APIs" under recent regulation.
What this means for you
You do not need to become an integration engineer. You need to recognise which standard is in play so you are not lost in a meeting. If someone mentions an interface engine, a MLLP connection, or a pipe-delimited message, that is v2. If someone mentions a resource, an endpoint, or a SMART on FHIR app, that is FHIR. Most organisations run both, often for years past when anyone planned to.