Most people know that driving under the influence of alcohol or drugs is dangerous — but driving with low blood sugar (called hypoglycemia) is also very dangerous. The worst outcome for people with diabetes who drive at the wrong time is to black out behind the wheel and kill or injure another person. Yet an online survey of more than 2500 Americans with type 2 diabetes found that about 19 percent had experienced hypoglycemia while driving.
“If something happens and they pull your blood sugar records and find out that you didn’t check before you drove, you can lose your license. I have seen some patients have their license taken away and it is very difficult to get it back,” warns Amy Kranick, a registered dietitian and certified diabetes educator with the adult diabetes program at Vanderbilt University Medical Center in Nashville, Tenn.
When Blood Sugar Dips
Hypoglycemia means that your blood sugar levels have fallen too low to support the needs of your body and brain. This is usually defined as less than 70 mg/dL. This dip in blood sugar is a possible side effect of some type 2 diabetes medications. Most people are aware of having low blood sugar and report that it is not a pleasant experience.
Symptoms include:
  • Headache
  • Dizziness
  • Sweating
  • Hunger
  • Tremors/trembling
  • Pale skin
  • Anxiety
  • Confusion
  • Changes in behavior or mood
  • Clumsiness
  • Difficulty paying attention
  • Seizures
  • Loss of consciousness

However, a few people with diabetes have “hypoglycemia unawareness” and don’t feel any symptoms until it is too late. This is why it is important to check your blood sugar before you take the wheel, just in case your numbers are going down and you have missed the signs or have not yet started to see the symptoms. The National Highway Traffic Safety Administration advises people who have hypoglycemia unawareness not to drive at all.

People with type 2 diabetes who take insulin are at increased risk for hypoglycemia as a side effect of this medication. Studies suggest that episodes of hypoglycemia become more frequent over time for these patients. A class of drugs called sulfonylureas, which lower blood glucose, can also cause hypoglycemia; common sulfonylureas include tolbutamide, glipizide, and glimepiride.
Planning Your Trips
Here is a basic outline of how to handle driving with diabetes:
  • Test blood sugar. “Don’t ever get in the car without checking your blood sugar,” emphasizes Kranick. Your blood sugar should be around 110 to 150 mg/dL.
  • Correct blood sugar. If your blood sugar is too low, do not get behind the wheel. Eat or drink one of the following and wait 15 minutes to check your blood sugar again:

    • 15 grams of a simple carbohydrate
    • 4 glucose tabs
    • 4 ounces of soda or fruit juice
  • Plan ahead. Keep healthy snacks in the car for emergencies. Make sure you have enough supplies for testing and correcting blood sugar in case you are stuck away from home for longer than you planned.
  • Check blood sugar regularly. If you are taking a long car trip, plan on checking your blood sugar every two to four hours. Make sure you have a stash of supplies to keep your blood sugar under control.
Driving with diabetes can be safe as long as you keep track of your blood sugar levels. Following these basic steps will keep you on the roads.