DVLA keep updating their guidance / rules if taking tablets and driving just a car, you only have to notify if you have had more than one hypo requiring assistance ie ambulance, doctor or friend that helps you recover from a hypo.
If on Insulin then you have to notify them asap, where they then restrict you to a max of a 3 year licence renewable. The rules for other classes of vehicles are different, where you have to notify them, when I was first diagnosed if one was on tablets I had to notify them.
You must how ever inform your insurance company, though it should not effect your premiums.