Watch out for hypoglycemia particularly if you exercise vigorously and take drugs with the potential to cause hypoglycemia, like insulin and sulfonylureas
If you take drugs that can cause hypoglycemia, you need to know about “hypoglycemia unawareness.” (Click for a quick review of diabetes drugs.)
Some people with diabetes, particularly after having the condition for many years, lose the ability to detect hypoglycemia just by the way they feel. This hypoglycemia unawareness is obviously more dangerous than being able to detect and treat hypoglycemia early on. Blood sugar levels may continue to fall and reach a life-threatening degree.
Hypoglycemia unawareness can be caused by impairment of the nervous system (autonomic neuropathy) or by beta blocker drugs prescribed for high blood pressure or heart disease. It’s more common in folks who have had diabetes for many years. People with hypoglycemia unawareness need to check blood sugars more frequently, particularly if driving a car or operating dangerous machinery.
Steve Parker, M.D.
Paleo Diabetic 
Please note that those diabetics who eat a very low carb diet can tolerate much lower blood sugars. For example, I’ve eaten a VLC diet for 11 years and had T1 for 50 years. During the past 11 years, I have had blood sugars in the 40’s and still functioned somewhat OK. At least, well enough to test and find sugary food. Though of course I stop hiking or biking until my sugar is back to normal.
There is more evidence that this is true. Many of the VLC diabetes that comment on various blogs say the same thing. Also, Dr. Steve Phinney described in one of his talks a study that tested that phenomenon. Healthy medical students were put on drips of ketones, insulin and glucose. They were able to function much better with more ketones when their blood sugars were artificially lowered.
Nate, thanks for that comment. I confess I’d never heard of that phenomenon.
Many folks get quite concerned when their serum glucose is under 60. I remember reading years ago that non-diabetics doing maximal exercise stress testing on a treadmill not uncommonly will drop their glucose to 45 without trouble. We believe they have to stop exercising at some point due to lactic acidosis and fatigue, not hypoglycemia.
-Steve