Technical Background

Introduction to FHIR

This guide is based on the HL7 FHIR standard, which is a platform specification that provides a common data model and API specification for exchanging health data. Because it is based on FHIR, this guide uses terminology, notations, and design principles that are specific to FHIR.

An abundance of information and resources are available for implementers looking to get started with FHIR. We recommend starting first with the FHIR Overview. FHIR's technical specifications are a major advancement, but its true value is in the community that has come together around it. If you have implementation questions, we highly recommend participating in the FHIR Online Chat platform and the FHIR Community Forum. The FHIR stewards are committed to fostering an open community, so all are welcome.


This guide uses conformance verbs, SHALL, SHOULD, and MAY, that have specific meanings that are defined in the FHIR Conformance Rules. Please review that reference page for more detail.

Must Support and Missing Data

This guide adopts the same guidance regarding data elements labeled as Must Support as the U.S. Core Implementation Guide on which it depends.

In short, a Responder SHALL populate such Must Support data elements in queries returned, and a Requestor must be able to process them.

Further guidance is provided in the U.S. Core Implementation Guide, including for circumstances where the source system does not have data for a Must Support data element or a required data element. For more information, please review these guidelines.

Privacy and Security

This guide does not add additional privacy and security requirements beyond those stipulated in the U.S. Core Implementation Guide. We encourage readers to review those provisions. In addition, there are two other important references that implementers should review and incorporate into their solutions:

  1. The FHIR Security specification provides guidance related to communication security, authentication, authorization/access control, audit, digital signatures, attachments, labels, narrative, and input validation.
  2. The FHIR Implementer’s Safety specification is a check list to help implementers be sure that they have considered all the parts of FHIR that impact their system design regarding safety.