In the U.K. diabetes is classed as a disability which may mean your employer has some extra responsibilities, based on medications you are taking.
This information is about how to manage diabetes at work and to support you in knowing your rights at work. Jump to:
www.diabetes.org.uk
Might be with reading up on this to see if there’s anything here that applies to your situation and being told to work alone on call.
Harbottle's right. Definitely read the material at the link he provided.
Andy: On the one hand, you do clearly need help improving your diabetes management. And, if you recently had a severe hypo, bad enough that you became unconscious and colleagues had to call an ambulance-- you need that help urgently. Your insulin regime clearly needs adjusting, and, as Helli says, you need a Libre.
On the other hand-- if this experience was recent, and nonetheless your employer is proposing to put you on "a callout rota which will involve lone working at remote sites"-- your employer must be out of its mind. No sane employer would propose this until and unless you had had help with your diabetes management *and* it had clearly worked, such that your diabetes consultant or GP was satisfied that it was safe for you to be working alone at remote sites. (And especially outside the normal working day; shift work is known to make it more difficult to manage diabetes.)
Do you have a union? If so, speak to them.
Does your employer have an Occupational Health department? If so, speak to them.
If neither, speak to your diabetes consultant or your GP and ask them if they will give you a letter to give to your employer.
It's a shame you have been put in this position, but I'm sure it can be sorted out. All best wishes!