As I understand things, being diabetic isnt in itself critical for self isolation, just that we are being encouranged/asked to distance ourselves i.e. not going to pubs, club social gatherings, hooking up with friends/family etc - to reduce our risk of catching anything.
However in the workplace, its a different story, especially doing a job like yours, you cant very well work from home and I can see being 'hands on' in your line of work would be a worry.....I guess you have to weigh up the risks. If you have other underlying conditions to consider. Whether or not you will be paid for taking voluntary absence from work could also be a hurdle for you? I would suggest maybe talk with your line manager.