FHIR Versions
The FHIR specification is under active development. Major updates to the FHIR specification are typically published every few years, and minor updates are published more frequently. The latest version, R5, was officially published in March 2023, and the next version, R6, is currently under development.1
The US Core Implementation Guide, which forms the basis of many US-based implementation guides and regulations, is currently based on R4. The US Realm Steering Committee (USRSC) has decided that the next version of FHIR which US Core will support is R6. Because US Core is skipping directly from R4 to R6, FHIR R5 is unlikely to be widely adopted in the U.S. Additionally, US Core will not support R6 until v11 (to be published in 2028) at the earliest. It would then take additional time for regulations and systems to be updated to use R6, so R4 is likely to remain the primary version of FHIR used in the US through 2030.
One of the major focuses in R6 is specification maturity. Major updates to FHIR can have breaking changes, but typically these changes only occur in areas of the specification that are not fully mature. FHIR uses a maturity model that describes “the level of stability and implementation readiness associated with different aspects of the specification.” More areas of the FHIR specification will be considered mature (or “normative” in FHIR parlance) after the R6 release.
Key portions of FHIR are already normative. For example, the Patient resource was assigned a normative maturity level in the R4 release of FHIR. This means that starting in the R4 release, the content of the Patient resource
is considered to be stable and has been ‘locked’, subjecting it to FHIR Inter-version Compatibility Rules. While changes are possible, they are expected to be infrequent and are tightly constrained.
The above description for normative as well as the other standards maturity levels can be found in the documentation on the standards development process.
Other resources, like NutritionProduct, have a lower maturity levels in the R4 and R5 releases. These resources are likely to experience more significant changes – including breaking changes – in R6 or subsequent releases of FHIR.
Implications for this website
References to resources and examples on this website typically use the Patient or Observation. Like Patient, Observation was normative as of FHIR R4, so the release of FHIR R5 and future versions is unlikely to affect these examples.
To ensure consistency between content in this website and links to the FHIR specification (or FHIR Implementation Guides), we link to version-specific pages whenever quoting from a specification or referencing material that might change in a future version. For example, we would link to the version-independent URL when generally referencing the Patient resource (https://www.hl7.org/fhir/patient.html), but would link to the R4 URL when stating that Patient achieved “normative” maturity in R4 (https://www.hl7.org/fhir/R4/patient.html). More details are in the Style Guide.
Due to these mitigation approaches, the content on this website should be relatively unaffected by new releases of the FHIR specification. However, if updates do need to be made, anyone is welcome to contribute.
Footnotes
To see the current status of R6, you can look at “R6 Sequence” section on the FHIR Specification’s Publication History page. There is also a release plan for R6.↩︎