• If you utilise iCloud to keep your old iPhone's Health up to date, your data will be automatically updated on your new iPhone whenever you're connected to Wi-Fi and signed in to iCloud. Go to Settings > [your name] > iCloud on both your old and new iPhones and make sure that Health is turned on.
• If you don't want to use iCloud, you can restore your previous iPhone from a PC backup. Make a new iCloud backup or encrypted computer backup if you still have your old iPhone and didn't erase it. After that, wipe your new iPhone and restore it from the backup. Reconnect your Apple Watch and iPhone if necessary. If you use a computer, be sure your backup is encrypted.

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