http://www.direct.gov.uk/en/Motoring...rs/DG_10030957 says:
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Drivers do not need to tell DVLA if their diabetes is treated by tablets, diet or both and they are free of the complications listed below.
Some people with diabetes develop associated problems that may affect their driving.
What you need to tell us about
By law you must tell us if any of the following apply:
- you need treatment with insulin
- you need laser treatment to both eyes, or in the remaining eye if you have sight in one eye only
- you have problems with vision in both eyes, or in the remaining eye if you have sight in one eye only. (By law, you must be able to read, with glasses or contact lenses if necessary, a car number plate in good light at 20.5 metres (67 feet) or 20 metres (65 feet) where narrower characters (50mm wide) are displayed)
- you develop any problems with the circulation, or sensation in your legs or feet which makes it necessary for you to drive certain types of vehicles only, for example, automatic vehicles or vehicles with a hand operated accelerator or brake. This must be shown on your driving licence
- you suffer more than one episode of disabling hypoglycaemia (low blood sugar) within 12 months, or if you or your carer feels that you are at high risk of developing disabling hypoglycaemia
- you develop impaired awareness of hypoglycaemia
- you suffer disabling hypoglycaemia at the wheel
- an existing medical condition gets worse or you develop any other condition that may affect your safe driving
In the interests of road safety, you must be sure that you can safely control a motor vehicle at all times.
How to tell us
If your doctor, specialist or optician tells you to report your condition to us, you need to fill in a DIAB1 medical questionnaire about diabetes.
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(Lots more to read, that's the highlights I've copied.)
Good luck.
Regards
Jim