What Are FHIR and HL7? A Clear Overview

Healthcare systems use different standards to exchange patient data. Two important ones are HL7 (Health Level Seven) and FHIR (Fast Healthcare Interoperability Resources). HL7 includes older versions like HL7 v2 and v3, and formats like CDA (Clinical Document Architecture). These have been around for decades, and many hospitals already use them for clinical messaging, administrative data, billing, lab results, and more.

FHIR, developed by the same standards body (HL7 International), builds on those earlier standards but is more modern. It is designed with web technologies in mind—APIs, RESTful architecture, JSON/XML/RDF formats. It breaks down healthcare data into smaller, reusable building blocks called “resources,” which makes exchanging and managing data more flexible.

How FHIR Differs from HL7 Version 2 and 3

HL7 v2 is quite mature and very widely used. It is message-based, using defined formats to transmit data between systems (for example, hospital systems, lab systems). It tends to be more rigid, legacy in style, and sometimes harder to integrate with newer tools without custom interfaces.

HL7 v3 and CDA tried to use more structured, document-oriented and model-based approaches (e.g., Reference Information Model, CDA). They tend to be more complex, and sometimes slower to adopt because of their strict schema and heavier overhead.

In contrast, FHIR simplifies many of those complexities:

• It supports RESTful APIs, which are more familiar to web/mobile developers.

• It uses lightweight data formats (JSON, XML, RDF) which are easier to work with than some older HL7 encoding schemas.

• Resources are modular, making implementations more flexible and incremental rather than all-or-nothing.

Data Interoperability: Why It Matters in Healthcare APIs

Interoperability refers to different systems being able to exchange and understand shared data correctly. In healthcare, that could be lab results, patient admissions, imaging reports, prescriptions, or even patient histories. Poor interoperability causes delays, errors, repeated tests, missing information, and less efficient care.

FHIR improves interoperability by enforcing clearer semantics, standard resource definitions, and modern data transfer methods. For example, rather than sending entire documents (like with CDA), FHIR allows retrieving specific data elements (a resource) via APIs. That means systems can get just the data they need, when they need it.

Ease of Implementation: FHIR vs HL7

When hospitals, clinics, or health systems decide to adopt a standard, how quickly and smoothly they can implement matters a lot.

With classic HL7 standards (especially older/customised HL7 v2 or v3 / CDA), integration often requires significant mapping, custom adapters, knowledge of legacy encoding, and sometimes handling numerous variants (because many institutions have slightly different “flavours” of HL7). This means more development time and more points of error.

FHIR is designed to reduce that friction:

• Its use of RESTful web APIs makes interfacing with modern web and mobile applications more straightforward.

• Its modular “resources” structure lets implementers adopt parts gradually rather than doing a full overhaul.

• Because many developers already know HTTP, JSON, and web frameworks, the learning curve is lower.

Which Standard Offers Better Support for Modern Tools & Apps

As healthcare becomes more digital, integration with mobile devices, cloud services, telehealth, wearable devices, and patient apps becomes essential. Also, data analytics, AI, real-time alerts, dashboards—all demand modern, flexible data exchange.

FHIR is better suited for these modern uses:

• It works naturally with web services, mobile apps, cloud platforms, IoT/wearables.

• Tooling for FHIR (libraries, existing APIs, community guides) is growing fast. This means development is faster, errors fewer, and updates more manageable.

• FHIR supports fine-grained data access, which helps when building dashboards, AI models, or just giving users specific parts of their health records (rather than entire documents).

On the other hand, HL7 (especially v2) remains very prevalent in legacy settings. It still handles many hospital internal workflows, lab messaging, and inter-system communication. For organisations with deep investments in HL7 v2, there may be cost and change management challenges in moving to FHIR.

Security and Compliance: Comparing FHIR and HL7

Patient data security is critical. Both HL7 and FHIR aim to support secure information exchange, but there are differences in how they integrate modern security practices.

• HL7 v2 and v3 were designed before modern web security frameworks and often rely on secure VPNs or HL7-specific transport protocols.

• FHIR, built with web technologies, supports contemporary security standards like OAuth 2.0, OpenID Connect, and TLS encryption.

• Using FHIR makes it easier to comply with regulations like HIPAA, GDPR, and local healthcare privacy laws because it aligns better with API-driven access control.

• APIs can be designed to share only what’s necessary, minimizing risk if data is exposed.

Handling Data Structure and Resources in FHIR vs HL7

The way data is structured impacts usability, integration, and scalability.

• HL7 v2 uses message-based formats where a single message contains multiple segments of data. This can be rigid and hard to extend.

• FHIR uses resources—modular, reusable building blocks (like Patient, Observation, Medication)—which are easier to implement, extend, and reuse across systems.

• Resources can be queried individually, which allows precise data retrieval and avoids sending unnecessary information.

• This modularity simplifies integration with multiple applications, dashboards, or analytics systems.

Scalability and Flexibility: Which Standard Adapts Better?

Healthcare systems are growing, and their IT infrastructures need to scale.

• HL7 implementations can be harder to scale due to rigid message formats and variations in how hospitals implement them.

• FHIR’s modular approach and RESTful APIs allow easier scaling. Developers can add new modules, apps, or integrations without affecting the entire system.

• FHIR supports cloud-based and mobile environments, making it more flexible for modern healthcare initiatives like telemedicine, AI-based analytics, or remote monitoring.

Cost & Time of Development: FHIR vs HL7 Trade‑offs

Time and cost of implementation are important for hospitals and clinics planning new API integrations.

• HL7 may require more custom coding, adapters, and specialized knowledge, which can increase cost and development time.

• FHIR’s standardised APIs, widespread developer familiarity with JSON/REST, and modular resources reduce development time and ongoing maintenance costs.

• Long-term, FHIR allows for faster updates, easier addition of new apps, and lower integration costs compared to legacy HL7 systems.

Real‑World Use Cases: Hospitals Choosing FHIR or HL7

Looking at practical examples helps illustrate the differences.

• Many hospitals maintain HL7 v2 for core internal workflows but adopt FHIR for new applications like patient portals, telemedicine, or mobile health apps.

• FHIR is increasingly chosen for real-time interoperability, integrating devices, EHRs, and cloud platforms, while HL7 handles traditional messaging like lab results and admissions.

• Hybrid approaches are common, letting organisations leverage the stability of HL7 and the flexibility of FHIR simultaneously.

Conclusion

Deciding between FHIR and HL7 for healthcare APIs involves weighing out what you have already, what you need now, and where you intend to go. If your organisation needs modern, flexible, web-friendly tools; wants to support mobile apps, patient portals, AI analytics, and quicker integrations, FHIR often offers clear advantages. But if you rely heavily on legacy systems, or existing HL7 interfaces already work well, the transition requires planning, investment, and potentially hybrid strategies (e.g. using both where appropriate).

If you’re evaluating the right standard for your healthcare API needs, or want expert guidance on implementing FHIR, integrating with HL7, or moving from one to the other, visit https://smartdatainc.com/. We can help you choose the path that suits your systems, your people, and your patients.