HL7 v2.5.1 Specifications
These specifications are an easier and more practical way to read the HL7 v2 documentation. They cover every concept in detail, with worked examples and an online HL7 Studio.
HL7 v2 is one of the most widely adopted healthcare messaging standards. Systems use it to exchange clinical and administrative data with each other.
Healthcare technology has changed a great deal since it was written. Newer standards such as HL7 FHIR now handle modern interoperability. HL7 v2 is still the one already installed almost everywhere.
A large number of healthcare systems already run on HL7 v2. If you work on healthcare interoperability, you will meet it.
What it covers
Whether you are looking for a message type, a segment or just a code table, we have covered each of them.
- 123 message typesacross 202 structures, showing which segments each one carries and in what order.
- 151 segmentseach with its full field table, in the standard's own column order.
- 90 data typesso you can see what is inside a field rather than only its name.
- 474 code tablesmarked as fixed by the standard or merely suggested, because only one of those makes an unlisted code an error.
- 278 trigger eventsthe real-world things that cause a message to be sent.
All of it comes from the official documentation. Getting an answer out of that is the hard part, and that is probably why you are here.
Why we built it
These specifications give you a modern way to read the official documentation. A field names its data type, and the type is one click away. Code tables and the segments inside a message structure work the same way. You can also open any example in HL7 Studio and change it.
The standard itself is a set of PDF chapters. The definition of a field, the data type it uses and the code table its values come from each sit in a different one. You end up with four PDFs open to answer one question. It is precise, and it was never built for looking things up.
It also does not say how to read it. There is no page telling you where to start or what to look at next. You are given a message and a specification, and left to work out how they fit together.
How to use these specifications reads one message from start to finish and shows where each part of it is explained.
Sources
Field definitions, code values and message structures are taken from the standard's own text and from the HL7 schemas. Anything we add on top of that is commentary, and every page marks it as commentary.
This site covers v2.5.1, published in February 2007 and still the version most production interfaces run.