You can check all types of notifications cf this question: 
BOOL remoteNotificationsEnabled, noneEnabled,alertsEnabled, badgesEnabled, soundsEnabled = NO;
// iOS8+
if ([[UIApplication sharedApplication] respondsToSelector:@selector(registerUserNotificationSettings:)]) {
     remoteNotificationsEnabled = [UIApplication sharedApplication].isRegisteredForRemoteNotifications;
     UIUserNotificationSettings *userNotificationSettings = [UIApplication sharedApplication].currentUserNotificationSettings;
     noneEnabled = userNotificationSettings.types == UIUserNotificationTypeNone;
     alertsEnabled = userNotificationSettings.types & UIUserNotificationTypeAlert;
     badgesEnabled = userNotificationSettings.types & UIUserNotificationTypeBadge;
     soundsEnabled = userNotificationSettings.types & UIUserNotificationTypeSound;
}
else {  // iOS 7 and below
      UIRemoteNotificationType enabledRemoteNotificationTypes = [UIApplication sharedApplication].enabledRemoteNotificationTypes;
      noneEnabled = enabledRemoteNotificationTypes == UIRemoteNotificationTypeNone;
      alertsEnabled = enabledRemoteNotificationTypes & UIRemoteNotificationTypeAlert;
      badgesEnabled = enabledRemoteNotificationTypes & UIRemoteNotificationTypeBadge;
      soundsEnabled = enabledRemoteNotificationTypes & UIRemoteNotificationTypeSound;
}
Then depending of the results, update your boolean on your backend by making a call to your API.