Hypoglycemia:

On the opposite end of the spectrum from hyperglycemia, hypoglycemia is an insufficient amount of sugar in the bloodstream, which may also be a problem for diabetics.  In addition to the buildup of fat creating more resistance from overabundant use of insulin, too much causes the sugar levels to plummet.  This can cause dizziness, blurred vision, fainting, coma or even death.  It is just as serious as hyperglycemia and the reason most diabetics carry a few small pieces of candy or glycerin pills with them, the latter tending to be more expensive but easier to take on jobs where eating is frowned upon or outright denied despite this being discriminatory to diabetics under the 1990 ADA regulations all businesses have to follow.  Most jobs will willingly comply to the needs of the disabled diabetic once reminded of this fact, though for obvious reasons they may insist on an understandable give-and-take of simply going into the backroom of such an establishment even if not on break to be able to get a quick piece of candy or the like to raise one's blood sugar.  This is perfectly legal and something I myself have to do at my work from time to time when my blood sugar drops.

One of the reasons that blood sugar drops, especially in type I diabetics is that their body absorbs the insulin they take to counteract the carbohydrates consumed, however the quantity they calculated for is actually lower than anticipated, rather than being significantly higher as is more often the case.  Those with type II diabetes rarely have this issue as their body is producing enough insulin but it is being resisted, however it can still happen to them and those who are not diabetic if an individual does not consume enough carbs in a day, typically something more common for people who are fasting.  This may also lead to diabetes, though more rarely than prolonged hypoglycemic period fouling up their body's regulation of insulin.