Hi paulfromgardiner!
I understand that the Health app isn't opening on your iPhone, and I'm happy to help. You can try closing and opening the app using these instructions:
How to force an app to close on your iPhone, iPad, or iPod touch
Also, please try restarting your iPhone:
Restart your iPhone, iPad, or iPod touch
If you're still having this issue, back up your iPhone before proceeding:
How to back up your iPhone, iPad, and iPod touch
Once you have backed up, you can reinstall the iOS software using this link:
If you can’t update or restore your iPhone, iPad, or iPod touch
If the issue is still present, try restoring the iPhone to factory settings and setting it up as a new iPhone:
Restore your iPhone, iPad, or iPod to factory settings
If this issue is present after restoring to factory settings, you can contact Apple Support using this link:
Contact Apple Support
Cheers!