Health information is very sensitive, and HealthKit gives its users full control over their data to decide which data is to be shared with the third-party apps, and which apps can share or use this data. Here, I will list some points to consider while working with HealthKit:
Don't use the information that is gained from HealthKit for advertising or other similar services.
You must not disclose any information gained to a third party without getting permission from the user. Even with permission, you can share this data only with those third parties that provide fitness or health services.
You can't sell information gained from HealthKit to any other service or platform.
You can share this information with a third party, for medical research, only if the user consents.