Yesterday Apple announced their health records API.
The documentation for it states that:
...clinical records are read-only, so you can’t request authorization to share clinical record types. You can’t create or save new HKClinicalRecord objects.
If I want to do some prototyping, and I don't work for one of the hospitals or clinics Apple currently supports, how can I load data into HealthKit to test reading and using this data in my app?
Beta 2 will have test accounts you can use from Simulator so you can test the integration with HealthKit. If you have specific FHIR patient data that you want to test with you can mock their delivery within your app.