Epidemiological studies looking at whether people with diabetes are at increased risk of motor-vehicle accidents (MVAs) have yielded conflicting results. Either increased risk, decreased risk, or no effect from diabetes has been reported.
Still, there are some reasons why governments have been concerned about the safety of people with diabetes driving, particularly if they are going to be driving with a commercial license such as a truck or school-bus driver.
The major concern is hypoglycemia. When a person's blood sugar level drops below 2.0 mmol/L (mM) their brain is not getting enough nutrition to function properly and they are at risk of having a reduced level of consciousness or seizure. This is of course dangerous if it occurs while someone is operating a motor vehicle. It has also been shown that driving performance is impaired when blood sugar levels are only mildly to moderately reduced (2.6 - 4.0 mM).
People with diabetes are also at increased risk of other medical complications which can impair their driving ability. This includes diabetic retinopathy, diabetic neuropathy, and macrovascular complications such as heart disease and stroke.
In Ontario the laws are such that physicians are obligated to report to the Ministry of Health any individual in whom they feel is unsafe to be driving. This is for their own safety as well as for the safety of others. Fortunately, most people with diabetes are safe to drive a car, even commercial vehicles such as trucks and school buses. The Canadian Diabetes Association (CDA) has set out guidelines for both private and commercial drivers. By following these guidelines, you and your diabetes health care team can insure that everything is being done to keep you safe behind the wheel.