If I uninstall/reinstall the application, do I lose my data?

Yes, the medical data is erased from the device when uninstalling the app. Uninstalling the application and reinstalling it will bring you back to the initial state of the application (plus your basic identification information, which is the only information kept on our servers). 

This is because your medical data is only stored on your device(s) and not on any server to guarantee the security and privacy of your data.

You may be able to recover your data after uninstalling the app if there is a copy of it somewhere. Refer to this article for more details: How to restore my data in Andaman7?