Which version should you be using?

The first question you need to ask is: are you targetting US organisations?

If the answer is yes, then you need to use FHIR R4.

You should NOT be using R4b, despite the fact that it’s the current release. You should NOT be considering R5, even if your app’s release date is expected to be later in the year, when R5 will likely be available.


On 31st December 2022 (just two months ago), the US Cures Act regarding FHIR came into effect. This Act mandates that healthcare organisations expose Patient data via a FHIR API.

But it goes further than that; it specifies the version number of FHIR that must be supported as R4 (4.0.1).

“API technology will be required to support the FHIR Release 4 standard, namely FHIR Release 4.0.1”

If your app uses R4b, you’re not in compliance.

If your app is released later in 2023 and uses R5, you will not be in compliance.

And if you’re not in compliance, your sales team is likely to have great difficulty selling your app to any US company or organization.

If your wider team and business is unaware of this, if your devs are working away assuming that the current version of FHIR (R4b) is the correct version to use, then you have a problem.

If you’re waiting on R5 because of new resources that will help your app, you will have a problem.

Cures Act final rule:

This is not something you can ignore. If the target user of your app is in the US, you need to use FHIR R4.



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