Practical Guide to Migrating from HL7 to FHIR

The healthcare industry relies heavily on reliable data exchange for efficient patient care and improved outcomes. HL7 standards have been reliable for sharing this information, but there are some limitations on the rise as healthcare data becomes more complex and interoperability needs to evolve. HL7 was among the first standards for interfacing and is completely event-driven. HL7 encompasses a suite of standards, with the most widely used being versions 2 and 3. These standards rely on complex message structures and specific data formats, often XML. This complexity can make implementation and integration challenging.

Various clinical events produce a specific type of HL7 message, which contains multiple segments. This data is characterized by a unique syntax and various reference sets. These characteristics create difficulties for developers for various operations. This is where FHIR (Fast Healthcare Interoperability Resources) steps in as a more modern, flexible standard.

While considering HL7 vs FHIR, FHIR is designed for simplicity and flexibility. It uses modern web technologies like RESTful APIs and supports multiple data formats, including JSON and XML. This makes FHIR easier to implement, integrate with existing systems, and adapt to evolving needs. In this blog, we will go through the complexities of migrating from the established HL7 standards to the more versatile FHIR framework, exploring the benefits and considerations associated with this migration.

The pressure to migrate is no longer abstract. When a major EHR deprecates an older API, as Cerner (Oracle Health) did with FHIR DSTU2 at the end of 2025, every product integrated against it must move to FHIR R4 (4.0.1) or lose its connection. For those teams, this stopped being a roadmap item and became a deadline.

HL7 v2 vs v3 vs FHIR: Which Version Are You Migrating From?

Before mapping a migration path, you need to know which HL7 version your systems actually run. Most healthcare organizations are on HL7 v2 it is the dominant format for hospital interface engines. HL7 v3 is rarely seen in production. FHIR R4 is the migration target for both.

For virtually all teams, “migrating to FHIR” means migrating from HL7 v2. The v2-to-R4 path is well-documented, has broad tooling support (Mirth Connect, HAPI, ConnectHealth), and is what the four-stage framework below covers. If your system runs HL7 v3, contact us, as the mapping approach differs and requires a custom assessment.

Understanding the Migration Process

Migrating from HL7 to FHIR is a significant undertaking that requires a well-defined plan and a thoughtful approach. To make this process easier to understand, let’s break down the key steps involved and add more details to each stage

Assessment

Assessment is an important step because it helps you understand where you are starting from and where you want to go. In the case of migrating from HL7 to FHIR, assessment helps you figure out what data you’re currently using, how it’s flowing, and what you need to do to make sure nothing important gets lost during the transition. It’s like knowing your starting point before you set off on a journey, so you can plan the best route to your destination. Here are some factors you need to assess before you start the process-

Data Flow

Identify the specific HL7 messages currently used (e.g., ADT – Admit/Discharge/Transfer, ORU – Order/Result) and the data elements exchanged within each message. Understanding the types of data being exchanged is crucial for planning the mapping process.

System Dependencies

Analyze which systems rely on HL7 data and how they utilize it. This could involve Electronic Health Records (EHRs), Lab systems, or Radiology Information Systems (RIS). Identifying these dependencies helps assess the impact of the migration on other systems.

Technical Infrastructure

Assess the technical capabilities of existing systems and compatibility with FHIR interfaces. Can your current systems handle FHIR-based data exchange, or will modifications be needed?

Organizational Readiness

Evaluate your organization’s resources and expertise in FHIR. This includes identifying any skills gaps and potential training needs for your IT team. Are your staff prepared to adopt and manage a FHIR-based system?

Related Video: Everything about HL7 in Easy Language👇

Planning

Once the assessment phase is complete, the next step is to develop a comprehensive migration plan. This plan serves as a roadmap for transitioning from HL7 to FHIR smoothly and efficiently. Here’s why planning is crucial and what it includes-

Scope

Define the specific functionalities and data elements to be migrated in this phase. You can choose a phased approach, migrating critical functionalities like patient demographics first and leaving less critical ones for later stages. This allows for a controlled transition and minimizes disruption.

Timeline

Set realistic timelines for each stage of the migration process, considering the complexity of the project and resource availability. Define clear milestones to track progress and ensure the project stays on schedule.

Resources

Identify the team members responsible for different aspects of the migration, including developers, system administrators, and clinical subject matter experts. Assigning clear roles and responsibilities ensures efficient execution.

Budget

Estimate the costs associated with the migration, including potential training, software licenses (if needed), and development resources. A well-defined budget helps secure necessary funding and manage project costs effectively.

Risk Management

Identify potential risks associated with the migration and develop mitigation strategies to address them. This could include data loss during migration, system downtime during deployment, or user resistance to change. Proactive risk management helps minimize disruptions and ensures a smooth transition.

Mapping

Once you have planned out your migration process, you can start with mapping. During the mapping stage, the focus is on establishing a clear translation process between HL7 and FHIR data formats. This ensures validated interoperability between systems. Here’s what this stage includes-

Analyze HL7 Messages

Break down the structure of each message and identify the data elements being exchanged. Understanding the structure of HL7 messages is crucial for finding corresponding elements in FHIR resources.

Identify Corresponding FHIR Resources

Find the appropriate FHIR resources (e.g., Patient, Medication, Observation) that represent the data contained within HL7 messages. Matching the data concepts in HL7 with the appropriate FHIR resource structure is essential for accurate data translation.

Map Data Elements

Establish a clear mapping between individual data elements in HL7 and corresponding fields within the chosen FHIR resources. Tools like the HL7 FHIR Mapping Guide can be helpful in this process. Use available resources to speed up the mapping process.

Custom Mappings

For complex data elements or scenarios not covered by existing mapping tools, develop custom mappings to ensure accurate data translation. Some data elements may require a more nuanced approach beyond pre-built tools.

Related Video: How FHIR Handles Crazy Complex Healthcare Data👇

Development

In this stage, you’re essentially laying down the technical groundwork needed to make the switch to FHIR smooth.

Initially, you’ll need to set up FHIR interfaces. These are like bridges that allow your systems or applications to talk to each other using the FHIR language. Whether it’s integrating with FHIR servers or utilizing cloud-based solutions, these interfaces ensure smooth communication.

Next comes data transformation. Think of this as translating from one language to another. You’ll need to implement logic that converts your existing HL7 data into the FHIR format, based on the mappings you’ve established. This might involve cleaning up the data and making sure it fits neatly into the FHIR structure.

System modifications are also on the agenda. Some of your existing systems might need some tweaking to understand and work with the new FHIR data. This could mean adjusting them to handle the new format and communication protocols.

By following these steps and considering the bigger picture, CTOs can craft a solid plan for migrating from HL7 to FHIR. It’s all about laying the foundation for a smooth transition that ensures your systems can continue to communicate effectively in the language of FHIR.

For Cerner (Oracle Health) Customers Post-DSTU2 Deprecation

Cerner deprecated DSTU2 endpoints in December 2025. If you’re on Cerner and still running DSTU2-dependent integrations, the migration path above applies with Cerner-specific notes:

• Cerner CODE re-listing: apps distributed through Cerner CODE need re-review on R4. Plan 4-8 weeks for the review queue.
• Resource mapping gaps: DSTU2 → R4 mapping for Patient + Observation is clean; CarePlan, MedicationOrder, and DiagnosticReport need transformation logic.
• OAuth scope changes: R4 uses patient/Patient.read, not DSTU2’s patient/.read. Update scope provisioning on all apps.

The Benefits of Migrating from HL7 to FHIR

While migrating from HL7 to FHIR requires careful planning and execution, the benefits for your healthcare organization can be significant:

Improved Data Exchange

FHIR’s use of modern web technologies like RESTful APIs and JSON makes data exchange faster, easier, and more reliable. This faster exchange fosters better communication and collaboration between healthcare providers.

Enhanced Interoperability

FHIR’s flexible resource model and standardized data formats enable tested integration with diverse healthcare IT systems. Improved interoperability allows data to flow freely between different applications, promoting a more holistic view of patient care.

Related Read: HL7 v2 to FHIR Conversion: The Complete Guide

Better Support for Modern Healthcare Needs

FHIR is designed to accommodate the evolving needs of the healthcare industry. It can handle complex data types and mobile health devices and integrates well with cloud-based solutions. This modern approach ensures your IT infrastructure can adapt to emerging technologies and healthcare trends.

Challenges and Considerations of Migrating from HL7 to FHIR

While the benefits of migrating to FHIR are compelling, it’s important to acknowledge the potential challenges involved:

Complexity of FHIR

Compared to the more structured message formats of HL7 v2, FHIR offers greater flexibility, which can also introduce complexity. The resource-based model and numerous data types may require a steeper learning curve for your IT team.

Lack of Internal Expertise

FHIR is a relatively new standard, and your organization might need more in-house expertise to manage the migration process effectively. This skill gap can create delays and hinder project execution.

Integration with Legacy Systems

Migrating from HL7 often involves integrating FHIR with existing legacy systems that may not be readily compatible with the new standard. This can necessitate modifications or workarounds to ensure seamless data flow.

Data Mapping Complexities

Mapping complex data elements from HL7 messages to corresponding FHIR resources can be a challenging task. While tools exist to assist, intricate data structures or custom elements might require manual intervention to ensure accurate translation.

Strategies to Address the Challenges:

Seek Training and Support

Invest in training for your IT team to build internal expertise in FHIR. Numerous resources are available, including online courses, workshops, and certifications offered by HL7 International and other organizations. Consider engaging FHIR experts for consultation or project guidance.

Use Available Tools and Resources

Use pre-built mapping tools and resources like the HL7 FHIR Mapping Guide to speed up the data mapping process. Explore open-source FHIR libraries and frameworks that can expedite development efforts.

Phased Approach and Prioritization

Break down the migration into manageable phases, focusing on critical functionalities like patient demographics in the initial stages. This phased approach allows for controlled implementation, and testing, and minimizes disruption to ongoing operations.

Clear Communication and Collaboration

Establish clear communication channels between IT, clinical teams, and other stakeholders throughout the migration process. Regular progress updates, workshops, and training sessions can foster collaboration and ensure everyone is aligned with the project goals.

By acknowledging these challenges and implementing the recommended strategies, CTOs can manage the migration process more effectively and minimize potential roadblocks.