All data remains ONLY on your phone and no data is EVER stored in the cloud. The app allows you to export CSV data or send PDF reports. In both such cases the app prompts you to send this data as an email attachment to yourself or your doctor. In other words the creators of this app or anyone else without access to your phone have absolutely no way of accessing your data.
The app has no registration process and users are never prompted for any kind of login. Data may only be accessed with physical access to users' phones.
No personally identifying info is ever collected by the app. There is an optional field to enter a first name which is stored only on your phone and appears only on the monthly report you may send to your doctor.
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