It’s not a simple answer and depends upon how your diabetes impacts on your life. The ‘reasonable adjustment’ rules foe employment apply to those with a disability, which is defined in the Equality Act as follows:
you have a physical or mental impairment
your impairment has a substantial and long-term adverse effect on your ability to do normal day-to-day activities
Some impairments are automatically treated as a disability, even if they don't affect your day-to-day activities. You’ll be covered if you:
have cancer, including growths that need removing before they become cancerous
are certified as blind, severely sight impaired, sight impaired or partially sighted
have multiple sclerosis
are HIV positive - even if you don't have any symptoms
have a severe disfigurement - for example severe facial scarring or a skin disease
In these circumstances then ‘reasonable adjustments’ should be made by the employer. You can read more here: