In MENU > Settings > Unit, you can change the units of weight, height and blood glucose.
The blood glucose unit is defined by default depending on the country entered when you created your iHealth account.
Note: You must connect the blood glucose meter to the app to apply the change on the device.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/360000452569-iHealth-Gluco-BG5S-Setting-units