what procedures are you thinking about?

for what type of employment?

how are they working alone from time to time?

why the pre-conception any employer should be doing anything?

does the employer actually know?

We have a type 1 in the family who works at their office job on occassion on their own (arrives early / leaves late), commutes/travels/hobbies etc on their own and no one at work knows - are you saying their employer needs to be involved?

You need lone working procedures that apply to anyone, recognising that some people may happen to have diagnosed or undiagnosed health conditions that could result in a health emergency, not only diabetes, but epilepsy, heart conditions, high blood pressure that could lead to a stroke ...

What those procedures are depend on the type of work, the working environment and what is practical, more than on an individual diagnosis.

Just because someone has a diagnosis of type 1 diabetes, it doesn't necessarily follow that it is more dangerous for them to work alone than for the next person.  If their diabetes is poorly controlled and they frequently have crises, it may be a different matter.

A company I worked for many years ago had a tanker driver with diabetes, and I don't recall any problems. It depends, of course, on how well it is controlled. There is a requirement to test before driving, and it has to be a reading of at least 5. I think the most you can do is have a conversation with the affected person to satisfy yourself that it is well controlled, as part of your duty of care. Beyond that, it is very much up to the individual.

The OP has not indicated which side this question is being approached from.

The assumption in replies is that the diabetic is another employee.

It could be they are being asked to conduct lone working and as a diabetic wish to know if their employer should be making specific arrangements.