Let me clarify. Blood glucose tracking has apparently been temporarily disabled. From AppleInsider:
Notably, display of blood glucose data has been temporarily disabled for the Health app as Apple works to add compatibility with devices that display the metric in mmol/L. Currently, the Health app does not allow manual input of data using that particular unit of measurement, so it will be removed to avoid confusion. While a fix is being engineered, third-party developers can still access the APIs, however.