HL7 (Health Level Seven)
Also called HL7 v2, Health Level Seven.
The standards body behind major health data standards, and the common name for its Version 2 messages that hospital systems use to exchange data.
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What it is.
HL7 stands for Health Level Seven. The organisation publishes several standards, including FHIR. When engineers say HL7, they often mean HL7 Version 2: text messages split into segments and fields, sent between systems when something happens, such as a patient being admitted or a lab result being ready.
HL7 v2 messages usually travel over an interface engine inside a hospital network rather than the public internet. Each site tends to use the standard a little differently, so every interface needs its own mapping.
Why it matters
Much hospital data still moves as HL7 v2, so a clinical product often needs to receive or send it even when the vendor also offers FHIR. Interface work can be a large share of a health integration's cost and timeline.
In a product build
We get sample messages from the site early, write the mapping per site, and keep every raw message so we can replay it. Incoming messages go through a queue and are handled idempotently, since interface engines resend on errors.
Common mistakes.
- 01
Assuming two hospitals send HL7 v2 the same way. Fields and codes differ by site.
- 02
Not storing raw messages, so bugs cannot be traced or replayed.
- 03
Starting interface work late. Hospital interface teams have long queues.
Read the official text.
Primary sources this definition is based on.
- HL7 FHIR specification (current published version)checked 2026-10-25
Work it out with a tool.
Related terms.
- FHIR (Fast Healthcare Interoperability Resources)A standard from HL7 for exchanging health data through modern web APIs, built from small, defined pieces called resources.
- EHR (electronic health record)A digital record of a patient's health and care that is built to be shared with other providers, so it can follow the patient.
- EMR (electronic medical record)The digital version of a clinician's paper chart: a patient's medical and treatment history kept within one practice.
- Message queueA buffer that holds messages, such as tasks or events, until a worker is ready to process them, so the sender does not have to wait.
- IdempotencyThe property of an operation that has the same effect whether it runs once or several times, so it is safe to retry.
