According to a report from CNET, it seems that there have been users in the UK and Australia who have reported issues regarding that particular feature. More specifically, this stems from a bug in which users not from the US are unable to enter their readings in their own measurements, which in the UK and Australia are millimole per litre, versus the US which uses milligrams per deciliter.
In a statement by Apple, “To prevent confusion in countries where mmol/L is commonly used, we’ll soon release a software update that will temporarily remove the ability to manually enter and view blood glucose values in the Health app while we work on an update to support both units of measurement.”
The feature will be removed in the next iOS update, but for those who have entered their current measurements and readings, those numbers will remain. Third party apps will still be able to input and access the data, so if you’re using third party apps to view the information, you will still be able to do so.