What is HL7 Integration? A Complete Guide for Healthcare Organizations

Healthcare data is complex, fragmented, and often locked inside siloed systems. HL7 integration is the bridge that connects those systems — allowing patient information to flow securely and reliably between electronic health records (EHRs), laboratories, pharmacies, radiology systems, and every other point of care.

In this guide, we'll explain what HL7 is, how HL7 integration works, the most common message types, how HL7 v2 compares to FHIR, and why healthcare interoperability is no longer optional for modern healthcare organizations.

What is HL7?

HL7 (Health Level Seven International)is a non-profit organization that develops and maintains a set of international standards for the exchange, integration, sharing, and retrieval of electronic health information. The "Level Seven" refers to the seventh (application) layer of the ISO Open Systems Interconnection (OSI) model.

HL7 standards define the structure, format, and content of messages exchanged between healthcare applications. The most widely deployed standard is HL7 v2.x, which has been in use since the late 1980s and remains the backbone of clinical system integration today. The newer HL7 FHIR (Fast Healthcare Interoperability Resources)standard takes a modern, API-first approach designed for today's internet-connected healthcare ecosystem.

What is HL7 Integration?

HL7 integration is the process of connecting two or more healthcare information systems using HL7 messaging standards to enable automated, bidirectional data exchange. When a patient is admitted to a hospital, for example, an HL7 ADT (Admit, Discharge, Transfer) message is automatically sent from the EHR to the lab, pharmacy, billing system, and any other downstream application that needs to know about that patient.

Without HL7 integration, each of these systems would require manual data entry — creating delays, errors, and HIPAA risk. With proper HL7 integration, data flows automatically and in real time, keeping all systems synchronized.

HL7 integration typically involves:

• An integration engine (such as Mirth Connect, Rhapsody, or Infor Cloverleaf) that receives, transforms, and routes HL7 messages
• Message parsing and transformation to map data between different HL7 versions and system-specific formats
• Connection interfaces using protocols like MLLP (Minimal Lower Layer Protocol), HTTPS, or direct TCP/IP connections
• Error handling and acknowledgment (HL7 ACK messages) to confirm successful message delivery

Common HL7 Message Types

HL7 v2 defines dozens of message types. Here are the most commonly integrated:

• ADT (Admit, Discharge, Transfer) — Patient registration and movement events. The most common HL7 message type.
• ORM/OML (Order Message) — Lab, radiology, and medication orders sent from the ordering system to the fulfillment system.
• ORU (Observation Result) — Lab results, pathology reports, and other clinical observations sent from the performing system back to the ordering system or EHR.
• SIU (Scheduling) — Appointment scheduling and scheduling notifications.
• MDM (Medical Document Management) — Clinical documents like discharge summaries, operative notes, and transcription reports.
• DFT (Detailed Financial Transaction) — Charge capture and billing data sent to financial systems.
• VXU (Vaccination Update) — Immunization records sent to or from immunization registries.

HL7 v2 vs FHIR: What's the Difference?

HL7 v2 and HL7 FHIR are both HL7 standards, but they take very different approaches to healthcare interoperability.

HL7 v2.xuses a pipe-delimited, text-based message format and is transmitted over MLLP or TCP connections. It's deeply embedded in hospital infrastructure — nearly every major EHR, lab system, and pharmacy platform supports HL7 v2. However, v2 lacks standardization across implementations (every vendor has their own "flavor"), making integrations time-consuming and brittle.

HL7 FHIRuses REST APIs, JSON/XML resources, and standard web protocols (HTTPS). It's designed for modern cloud-based applications, patient-facing portals, mobile apps, and the new wave of digital health. FHIR is the standard required by the ONC Final Rule and CMS Interoperability Rule, and it powers the App Orchard (Epic) and SMART on FHIR ecosystems.

In most healthcare organizations today, both standards coexist: HL7 v2 handles real-time clinical messaging between internal systems, while FHIR powers modern API-based access for patient portals, third-party apps, and regulatory reporting.

Benefits of HL7 Integration

Proper HL7 integration delivers measurable benefits across clinical, operational, and financial dimensions:

• Eliminated manual data entry — Automated message flows replace manual transcription, reducing errors and staff burden.
• Real-time clinical data availability — Clinicians see up-to-date lab results, orders, and patient information without switching systems.
• Improved patient safety — Automated alerts, duplicate order detection, and allergy checking reduce adverse events.
• Faster revenue cycle — Automated charge capture, eligibility verification, and claim submission accelerate reimbursement.
• Regulatory compliance — Meeting ONC, CMS, and state HIE requirements for data sharing and patient access.
• Scalability — A well-designed HL7 integration architecture grows with your organization without requiring rework.

How to Get Started with HL7 Integration

Starting an HL7 integration project requires careful planning. Here's the typical path:

1. Assess your current systems — Inventory your EHRs, ancillary systems, and data flows to identify integration gaps.
2. Define your integration requirements — Which message types do you need? Which systems need to communicate? What are your data transformation needs?
3. Choose your integration engine — Mirth Connect (open source), Rhapsody, Infor Cloverleaf, Azure Health Data Services, and AWS HealthLake are common options.
4. Design your interface architecture — Define message schemas, routing rules, transformation logic, and error handling before writing any code.
5. Build, test, and validate — Rigorous testing with real message samples is essential. Never go live without clinical validation.
6. Monitor and maintain — Live integrations require ongoing monitoring, alerting, and maintenance as systems and standards evolve.

Working with an experienced HL7 integration partner can dramatically reduce the time, cost, and risk of your integration project. Our team at HL7 Integration Solutions has delivered 500+ healthcare integrations and can help you design, build, and maintain the right solution for your organization.