What is X12 EDI?
X12 EDI is the earliest mainstream digital medical standard, primarily used for medical claims in the payer portion of the healthcare industry.
Despite being over 45 years old, X12 EDI remains the main method by which claims are transmitted between entities to manage medical payments.
A portion of an 837 X12 EDI Healthcare Claim
Some additional information:
X12 EDI messages are strings of text called ‘transactions‘. The spec does not define how they are to be transferred, just structured. There are about 300 transaction types, only about 20 of which are used for healthcare.
X12 EDI messages are used for things outside of healthcare. It is also used in transportation, finance, government (including disability management), and logistics for business-to-business communication.
The X12 spec is a closed / private standard, despite being ANSI ‘chartered‘. This means that to use the spec, or view how it is managed in its most recent version, you must pay a license fee to X12. It also means there are no complete open source tools to cleanly digest or manipulate them.
HL7v2 ADT was largely built off the X12 EDI standard. There are heavy similarities in how the two are structured. X12 EDI has more segment types, whereas HL7v2 ADT has more basic data types.
X12 EDI may be converted to FHIR. Just like HL7v2 ADT messages, X12 messages contain healthcare data that may be converted into FHIR resources and bundles.
X12 EDI Structure
The Structure of X12 EDI files is more complicated than HL7v2 ADT. Of the 300 transaction types, each is narrowly defined in how they are structured.
Transactions are the main unit. A group of transactions may be sent together in a “Functional Group“. A group of functional groups is called an “Interchange“. There are about 300 transaction types.
Loops are subdirectories inside of transactions which may repeat. They are viewed within the context of their parent data outside of them. Loops can contain loops. The loops in a transaction are defined by the transaction type.
Segments are dictionary elements with key-value pairs. For example, a patient segment describes their name and address across multiple fields. There are about 1000 segment types.
Basic Datatypes are the the types of data that make up segments. these include string, numeric, decimal, date, time, id (code), and binary.
X12 EDI to HL7 FHIR
X12 EDI conveniently may be converted to HL7 FHIR via Tenasol. There is no standard specifying how to do this because of the X12 specifications private nature. However, we have taken the time to convert the following transactions via API or bulk transfer:
267 Individual Life, Annuity and Disability Application
269 Health Care Benefit Coordination Verification
270 Eligibility, Coverage or Benefit Inquiry
271 Eligibility, Coverage or Benefit Information
274 Healthcare Provider Information
275 Patient Information
276 Health Care Claim Status Request
277 Health Care Information Status Notification
278 Health Care Services Review Information
500 Medical Event Reporting
834 Benefit Enrollment and Maintenance
835 Health Care Claim Payment/Advice
837 Health Care Claim
837P Health Care Claim - Professional
837I Health Care Claim - Institutional
Clients interested in converting X12 EDI to FHIR can benefit from substantial growth of their HL7 FHIR data lake, especially when combined with Tenasol’s other HL7 FHIR transformation services for PDF data, ADT / HL7v2 data, and CCDA data, and be able to perform graph data analysis.
X12 EDI to Other Formats
It is a rare need to convert X12 EDI to HL7v2 (ADT) or HL7v3 (CDA). This is because the latter two formats are typically used for different purposes. HL7v2 is more common within the provider domain, whereas X12 EDI is more common in the payer domain. They also typically focus on different information, so have little overlap and therefore conversion is of little use. To view more information on medical data format conversion see our blog on the subject.
Conclusion
X12 EDI remains a cornerstone of medical data exchange, especially in the payer segment of the healthcare industry. Despite its age and the complexity of its closed specification, it continues to power the transmission of critical claims and administrative data. With limited overlap between X12 EDI and provider-facing standards like HL7v2 or HL7v3, the most valuable transformation pathway today is from X12 to HL7 FHIR. This unlocks modern interoperability, analytics, and patient-centric care workflows.
While working with X12 can be daunting without access to the full specification, solutions like Tenasol simplify the process by converting key transaction types into clean, usable FHIR resources. As healthcare continues to evolve toward value-based care and integrated ecosystems, enabling X12 data to participate in broader FHIR-based data lakes will be essential for insights, automation, and better health outcomes. For teams seeking to bridge legacy and modern standards, X12-to-FHIR conversion offers a powerful path forward.