If you have a hypoglycemic event  whilst driving:

• Stop the vehicle as soon as possible
• Switch off the engine, remove the keys from the ignition and move from the driver’s seat
• Take some fast-acting carbohydrate, such as glucose tablets or sweets, and some form of longer-acting carbohydrate.
• Do not start driving until 45 minutes after blood glucose has returned normal.

If you have poor warning signs, or have frequent hypos, you should probably not be driving because of the risk to yourself and others. Discuss this with your doctor. If he advises you to notify the DVLA/DVA you must do so. If you fail to do this, your doctor has an obligation to do so on your behalf.