Do You Need a Custom HL7 Interface Built From Scratch?

Key Takeaways

• You need a custom HL7 interface when standard integration tools cannot meet your requirements for data mapping, workflows, or message exchange. 
• This can be helpful when working with older systems or several healthcare platforms at once.
• However, a ready-made interface engine may be enough for simpler integration needs.
• If you’re planning a custom HL7 interface, IdeaUsher can help you build and integrate it with your healthcare systems.

You need a custom HL7 interface when your project involves multiple EHRs or requires specific data mapping and FHIR support. Building a custom HL7 interface from scratch requires analyzing data, writing parsing and error-trapping code, and managing point-to-point connections 

Different systems can use different data formats and may need custom rules to exchange information correctly. We’ve built various custom HL7 interfaces for healthcare businesses, and in this blog, we’ll explain when building one from scratch makes sense and what you should consider before getting started.

Is a Custom HL7 Interface Worth the Investment?

Yes, a custom HL7 interface can be worth the investment when your healthcare platform has integration needs that standard tools cannot handle well. It can give you better control over how data moves between systems and make it easier to support your own workflows. The market is also moving toward more advanced interoperability. According to Spherical Insights, the global HL7 FHIR compliance market is valued at around $2.21 billion and expected to reach about $7.24 billion with a 12.6% CAGR.

Source: Spherical Insights

Save Time Long Term

A custom interface may take more work at the start but can save time as your platform grows. You can build it around your workflow instead of changing your system whenever a standard connector falls short. This is especially useful with multiple EHRs. Different vendors can use different message structures and rules, so a custom interface gives you more control over these differences.

Wellstar Health System uses Redox to move data from its Epic EHR into Microsoft Healthcare APIs. The setup handles around 8 million messages per month. Wellstar also reported more than $3 billion in revenue, showing the scale at which healthcare interoperability can operate. 

Improve Data Flow

A custom interface can reduce manual work when healthcare systems do not communicate properly. Orders can move between systems while results can return to the EHR without repeated data entry. It can also help teams track failed messages and handle retries. This makes it easier to find problems before they affect the workflow. The main benefit is consistency. Data follows a clear path and teams spend less time fixing integration issues.

Juno Health uses HL7 FHIR APIs and standards-based data coding for interoperability. It also partnered with Avo to bring AI-powered clinical documentation into its EHR system. This shows how strong interoperability can support new healthcare features.

Plan for Growth

A custom HL7 interface becomes more useful as your platform adds healthcare partners and data sources. Instead of creating a new solution for every connection, you can build an integration layer that supports future systems. Health Gorilla provides access to 220 million+ patients, 120,000+ care sites, and 120+ integrated lab vendors. Its platform supports FHIR APIs along with HL7 v2 ADT messages and other clinical data workflows. 

For a growing healthcare business, the interface should work for both your current needs and future integrations.

A scalable interface can help you:

• Add new healthcare systems
• Support HL7 and FHIR workflows
• Handle higher message volumes
• Add new transformation rules
• Keep integration logic organized
• Prepare for future interoperability needs

Do You Need to Build the Custom HL7 Interface From Scratch?

Not always. A standard connector or interface engine may work well when your healthcare systems use common HL7 structures. Building from scratch makes more sense when you have unusual workflows, vendor-specific messages or several systems to connect. The right choice depends on what your integration actually needs.

1. Your EHR Sends Non-Standard HL7

HL7 gives healthcare systems a common way to exchange information. Still, different EHR vendors can structure their messages in different ways. They may also use optional fields differently or add their own rules. This can create problems even when two systems use the same HL7 version.  A custom mapping layer can help your application handle these differences without changing the rest of your system.

It can help you:

• Map vendor-specific fields
• Handle different message structures
• Convert local codes
• Support different HL7 versions
• Use one format across several EHRs

2. Your Workflow Uses Z-Segments

Z-segments are locally defined HL7 segments. Hospitals and vendors can use them to carry information that is not part of the standard message structure. If your application needs this extra information for routing or transformation, then a standard setup may not be enough. InterSystems also notes that custom schemas can be used when Z-segment fields are needed in routing and data transformations. 

3. One Interface Serves Multiple Systems

Connecting one EHR to one application is much easier than connecting several EHRs, labs and healthcare systems. Each connection may have its own message rules. A custom integration layer can keep these differences in one place.

Epic shows how large interoperability can become. Its Care Everywhere network exchanges around 30 million patient record documents each day and Epic reports 923 million records exchanged per month. 

4. Standard Connectors Miss Your Mapping

Standard connectors work well when the data already matches what your application needs. Problems can appear when fields need to be renamed, converted or combined before use. athenahealth provides packaged HL7 connections for common needs such as laboratory and imaging systems. It also offers APIs for custom integrations when standard options are not enough. 

This shows that you do not always have to choose between standard and custom development. You can use existing interfaces where they work and add custom logic where needed.

5. Your App Needs More Logic

Sometimes the problem is not the HL7 message itself. Your application may need to decide where a message goes or what happens after it arrives. A simple converter may not be able to handle these rules. A custom integration layer can help your application:

• Route messages based on their content
• Apply validation rules
• Transform data before delivery
• Trigger actions after receiving messages
• Connect HL7 with APIs or FHIR

6. You Need Better Control

Healthcare integration also needs to handle failed messages. Your system should be able to track what happened and retry a failed transaction without losing important data. Oracle Integration for Healthcare supports multiple HL7 v2 versions and can process messages in the order they are received. 

HCA Healthcare reported $75.6 billion in revenue and continues to invest in its EHR infrastructure. Its MEDITECH Expanse rollout covers 50 acute-care facilities as of January 2026. For healthcare businesses operating at this scale, stronger control over integration can make future system changes easier.

7. Your Platform Is For Healthcare

If you are building a healthcare product that connects with EHRs for many customers then the integration layer can become part of the product itself. You may need HL7 v2 for one customer, FHIR for another and custom mapping for someone else. Oracle Health is a good example. Its interoperability platform supports HL7 v2, C-CDA and FHIR. Oracle Health Information Network also received QHIN designation under TEFCA. 

Custom HL7 Interface vs Interface Engine: What Should You Build?

Choose a custom HL7 interface when your healthcare platform needs workflows or data handling that an interface engine cannot support. An interface engine is usually a better choice when you need to connect several systems without building everything yourself. For simple connections, a point-to-point interface may be enough. The best option depends on your integration needs and how much control you want. 

Build a Point-to-Point HL7 Interface

A point-to-point interface connects one healthcare system directly to another. It works well when you have a small number of systems and a simple data flow. The setup is also easier to start with. However, every new connection adds another interface to maintain.

Best fit: Simple workflows with a limited number of systems.

Configure an HL7 Interface Engine

An interface engine gives you one place to receive, transform and route HL7 messages. This makes managing several healthcare connections easier. Many engines also support validation, routing and monitoring. ONC research found that 9 in 10 hospitals integrated data from third-party technology into their EHR for at least one clinical purpose. Much of this exchange still uses HL7 interfaces rather than only modern APIs.

Customize an Existing Interface Engine

You can also start with an existing engine and customize the parts your workflow needs. This may include mapping, routing, transformations and API or FHIR connections. It gives you more control without building every component from scratch.

This approach works well when:

• The engine supports your HL7 version
• You need custom transformations
• Several systems share data
• You need centralized monitoring
• Your workflow needs extra business rules

Memorial Hermann invested around $500 million in its EHR transformation and moved to Epic across 15 hospitals and 250 care sites. The project also used Epic’s Care Everywhere platform to support interoperability.

Build a Dedicated Healthcare Integration Layer

A dedicated integration layer makes sense when interoperability is part of your healthcare product. It can bring HL7, FHIR, and APIs into one architecture. This gives you more control as you add EHRs and healthcare partners. Union Health has annual revenue of just under $1 billion and began moving from Oracle Health to Epic to improve data sharing and reduce operating costs. The transition also required major IT resources. 

Which Approach Fits Your Business?

The decision mainly comes down to complexity and future growth. A point-to-point interface can work for one simple connection. An interface engine is better for several systems. If interoperability is central to your healthcare product, a custom integration layer can provide greater control as you grow.

Which HL7 Workflows Usually Require Custom Development?

Custom development is most useful when a healthcare workflow needs more than basic message exchange. This often happens when systems use different data structures or when one workflow involves several platforms. Simple connections may work with standard interfaces. More complex workflows often need custom mapping, routing or transformation.

1. EHR to Laboratory System Integration

Lab integration often needs custom work because EHRs and LIS platforms do not always use HL7 in exactly the same way. An EHR may send an ORM order while the LIS returns an ORU result. Patient IDs, test codes, and result structures may also need to be mapped before the information reaches the patient’s chart.

A research study found that the HL7 ORU message in version 2.5.1 contains 4,132 data elements. The implementation guide created for outpatient laboratory reporting reduced the optional elements by 93%, showing how much variation can exist in real-world lab interfaces. 

2. EHR to Radiology and PACS

Radiology workflows usually connect the EHR or RIS with PACS. HL7 can carry patient, order and result information while the imaging system handles the actual medical images. A custom interface may be needed when the workflow requires specific routing or when the result needs to include a PACS viewer link.

Typical flow:

EHR → ORM → RIS → PACS → ORU → EHR

3. Hospital to Billing or Claims

Billing workflows can involve clinical data as well as financial information. Patient details, procedures and charges may need to move between the EHR, hospital billing system and payer. Depending on the setup, this can involve HL7 messages such as DFT along with FHIR financial resources such as Claim and ClaimResponse. 

This becomes more complex when the hospital needs to connect several financial systems. A custom integration can help apply the right mapping and business rules before financial data reaches the next system.

4. Healthcare App to EHR Integration

A healthcare application may need access to patient records, appointments, medications or clinical results from an EHR. Modern applications often use FHIR APIs for this type of access, while HL7 v2 can still be needed for events such as ADT, orders and results. This means the application may need to work with both approaches.

5. Multi-EHR Integration for SaaS

A healthcare SaaS platform has a harder problem because it may need to support several EHRs at once. One customer may use Epic while another uses a different EHR. Their HL7 messages and API capabilities may also differ. A custom integration layer can keep these differences away from the main application.

The scale can become significant. CommonSpirit Health has reported more than 10,000 active interfaces across its environment and uses both traditional HL7 integration and modern API-based patterns. Its integration strategy covers Epic Bridges, Cerner and other enterprise systems. 

6. Lab and Diagnostic Results

Diagnostic workflows can require more than simply sending a result back to an EHR. A system may need to handle corrected results, different reference ranges, abnormal values and multiple observations within one report. ORU messages are commonly used to deliver these results.

For modern platforms, these results may also need to be converted into FHIR resources such as DiagnosticReport and Observation. This makes custom transformation useful when a platform needs to support both older HL7 feeds and modern APIs. 

7. Legacy HL7 Systems With APIs

Many healthcare organizations cannot simply replace their older HL7 systems. They need to connect them with newer applications that use REST APIs and FHIR. This creates a need for a layer that can translate between the older message-based workflow and the newer API model.

Ascension provides a good example. Its Enterprise Data Service Layer creates an abstraction layer for normalized clinical, consumer and operational data while supporting HL7 FHIR. Ascension reports $25.3 billion in total revenue, 90 wholly owned or consolidated hospitals and 97,300 associates, making this type of integration important across a large and varied healthcare environment.

How to Build a Custom HL7 Interface From Scratch?

Building a custom HL7 interface starts with understanding the receiving system. You then define the messages, map the fields, and add the logic needed to process them. Testing with real vendor messages is important before launch. Monitoring helps keep the interface reliable after deployment.

1. Start With the Implementation Guide

Get the receiving system’s implementation guide before writing code. It explains the HL7 version, messages, fields, and rules the system expects. HL7 guidance recommends documenting the specific interface profile instead of relying only on the base HL7 standard. This matters because two systems can use the same HL7 version but still have different requirements. Victoria’s Digital Health implementation guide, for example, defines specific requirements for pathology, imaging, medications, and patient administration. 

2. Define Messages and Events

Decide what data needs to move and what event will trigger it. HL7 v2 uses trigger events to define when messages should be sent. 

Defining these flows first makes the development process clearer.

3. Map Every Source Field

Map data from the sending system to the receiving system. A field with the same name may not have the same meaning in both systems. Patient IDs, provider codes and clinical codes may need transformation. One laboratory interoperability study tested its implementation guide across 15 organizations and reduced optional data elements by 93%. 

Your mapping document should cover:

• Source and destination fields
• Data type
• Required status
• Transformation rules
• Allowed values
• Error conditions

4. Separate Parsing From Logic

Keep HL7 parsing separate from your business rules. This makes the interface easier to test and update when an EHR changes its message format. It also helps when the same data needs to reach different systems. For example, one destination may use HL7 while another uses a FHIR resource.

5. Build Validation and Recovery

Validate messages before sending them to the destination. Check required fields, identifiers, data types and codes. HL7 guidance also recommends defining how acknowledgements should work. If a message fails, do not simply drop it. Record the error and give your team a way to review and recover the transaction.

6. Add ACK and Retry Logic

HL7 commonly uses ACK and NACK messages to show whether a message was accepted or rejected. Google Cloud Healthcare API, for example, returns an ACK when HL7v2 ingestion succeeds and a NACK when an error occurs. Your interface should also handle temporary failures. Queues and retry rules can help prevent clinical messages from being lost during network or system problems.

7. Test With Real Messages

Use real messages from the EHR or healthcare system during testing. Generic HL7 examples may not match the vendor’s actual implementation. GE Healthcare recommends testing individual transactions as well as complete workflows. 

Test for:

• Valid messages
• Missing fields
• Invalid identifiers
• Duplicate messages
• ACK and NACK responses
• Network failures
• High message volumes
• End-to-end workflows

8. Monitor Before and After Launch

Monitoring should be built into the interface from the start. Track message volume, processing time, errors, and ACK/NACK responses so your team can find problems quickly. One healthcare interface case study reported 312,480 messages per day across more than 80 HL7 and FHIR interfaces. Its monitoring system helped recover $3.6 million in annual charge leakage.

How Much Does a Custom HL7 Interface Cost?

A custom HL7 interface can cost anywhere from $10,000 to $100,000+ depending on what you need it to do. A simple one-way connection costs much less than a bidirectional interface with complex mapping and several EHRs. You should also plan for testing, monitoring, and maintenance instead of looking only at the initial development price.

What a Basic HL7 Interface Includes

A basic HL7 interface usually connects two systems and handles a limited number of message types. It may include message parsing, field mapping, validation, testing and basic error handling. Current industry estimates put a single one-way HL7 v2 interface at around $10,000–$20,000, while a bidirectional setup can reach $25,000–$45,000.

The final price depends on the number of messages, mapping rules, and systems involved.

What Makes an Interface More Expensive?

The cost rises when the interface has to do more than move standard messages. Vendor-specific formats, custom Z-segments, complex transformations and bidirectional workflows all add development and testing work. Security requirements and EHR certification can also increase the budget.

A full custom HL7 interface suite can reach $50,000–$250,000+ when several workflows and systems are involved.

Common cost drivers include:

• Custom message mapping
• Multiple HL7 message types
• Z-segments and local codes
• Bidirectional data exchange
• Error and retry handling
• EHR certification
• Security and audit requirements
• Testing with real clinical data

How Multiple EHRs Change Cost

Adding another EHR does not simply mean adding another connection. Each system may have different APIs, HL7 profiles, and mapping rules. A healthcare platform supporting two or three EHRs can therefore require a much larger integration layer. Current planning estimates place multi-EHR integration at around $80,000–$150,000+ for two or three platforms.

For example, a healthcare SaaS product might spend around $30,000 on one basic HL7 connection but need $100,000+ once several EHRs, patient matching and bidirectional workflows are added.

Does FHIR Increase Development Cost?

Adding FHIR can increase the initial development cost because your team may need to support APIs, resource mapping, authentication and different data models alongside HL7. A single read-only FHIR connection can start around $15,000, while bidirectional multi-resource integration can reach $50,000–$150,000+.

FHIR can still be a useful investment when your product needs modern APIs while continuing to work with healthcare systems that rely on HL7 v2.

What Will Maintenance Cost?

HL7 integration does not end when the interface goes live. Your team may need to handle EHR changes, mapping updates, security patches, failed messages and monitoring. Current industry estimates put ongoing maintenance at around $3,000–$15,000 per interface each year.

For a healthcare business with five live interfaces, that can mean roughly $15,000–$75,000 per year in ongoing interface maintenance before other infrastructure or licensing costs.

Custom Interface vs Interface Engine: Lower TCO?

The cheapest option at the start may not be the cheapest over three years. A point-to-point interface can work well for one or two stable connections. An interface engine becomes more useful as the number of integrations grows, while a custom integration layer can make more sense when interoperability is part of the product itself.

Build Your HL7 Interface In-House or Outsource It?

You can build a custom HL7 interface in-house if you already have a skilled healthcare integration team. Outsourcing may be better when you need HL7 expertise without building a dedicated team. The right choice depends on your skills, project size and long-term support needs.

What an In-House HL7 Team Must Handle

An in-house team needs to handle more than HL7 coding. Developers must understand EHR workflows, data mapping, FHIR APIs and healthcare security. They also need to test, monitor and maintain the interface after launch. A healthcare study found that 68% of organizations saw a lack of well-trained IT staff as a health IT challenge. Another 53% identified interoperability as a challenge. 

A research report on a German hospital network also found that its unified IT structure supported an EHR data platform across 77 hospitals. 

When Outsourcing HL7 Makes Sense

Outsourcing can help when you need specialized HL7 skills without hiring a full team. It can also make sense when your developers are focused on your main healthcare product. ONC research found that 92% of digital health companies had integrations with at least one EHR and 78% were working with two or more EHR vendors. Among companies working with multiple EHRs, 73% reported extensive use of FHIR.

Outsourcing can help when you need:

• Custom HL7 development
• EHR and FHIR expertise
• Multiple healthcare integrations
• Complex data mapping
• Testing and monitoring
• Ongoing maintenance

What to Expect From a Partner

A good HL7 partner should handle more than development. They should understand the EHR’s implementation guide, create the required mappings and test real messages. They should also provide support after the interface goes live. The American Hospital Association identifies EHR integration and interoperability as ongoing IT challenges for healthcare providers. 

Look for experience with:

HL7 v2 → FHIR → EHR/EMR → Mapping → Testing → Monitoring

Questions to Ask Before Hiring

Before choosing a development partner, ask how they will handle your EHR and vendor-specific requirements. You should also know how they will manage testing, failed messages, and maintenance.

• Have you built custom HL7 interfaces before?
• Can you work with our EHR or EMR?
• How do you handle Z-segments?
• Can you support HL7 v2 and FHIR?
• How will you test the interface?
• How are failed messages handled?
• Who maintains the interface after launch?
• Can it support more EHRs later?

If you want to outsource custom HL7 interface development, IdeaUsher can help you design and build the interface for your healthcare platform. The team can support development, testing, deployment and ongoing improvements.

Why Choose IdeaUsher for Custom HL7 Interface Development?

IdeaUsher can help you build a custom HL7 interface around your healthcare platform’s needs. Our team handles HL7, FHIR, EHR and EMR integrations along with custom data mapping. We can support your project from planning and development to testing and deployment.

Healthcare Integration Expertise

Healthcare integration needs more than basic HL7 coding. Our team understands healthcare data flows and the challenges of connecting different systems. IdeaUsher has 500,000+ hours of coding experience. Our team also includes ex-MAANG and FAANG developers with experience in complex technology projects.

HL7 and FHIR Development Capabilities

We develop solutions using HL7 v2 and FHIR based on your integration needs. This can include message parsing, validation, transformation, routing and API-based data exchange. Whether you need a simple HL7 interface or a combined HL7 and FHIR setup, we can build it around your use case.

EHR and EMR Integration Experience

Every EHR and EMR can have different implementation rules and data requirements. Our team can help connect your platform while handling data exchange, authentication, message processing and testing. This helps your application work smoothly with the healthcare systems your users already use.

Custom Mapping and Transformation

Different healthcare systems may structure the same data in different ways. We create custom mapping and transformation rules to move that data correctly. Our team can also handle vendor-specific HL7 messages, Z-segments, custom fields and complex data flows when standard connectors are not enough.

Conclusion

A custom HL7 interface can be the right choice when standard tools do not fit your healthcare platform. It gives you more control over how your systems share data and handle your workflows. Before building from scratch, check what your current systems need and whether an existing solution can do the job. If you decide to build a custom interface, IdeaUsher can help you take it from planning to deployment. 

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